Merge pull request '4-implement-scene-switching-engine' (#4) from 4-implement-scene-switching-engine into master

Reviewed-on: #4

docs/4-implement-scene-switching-engine.md

@@ -0,0 +1,91 @@
+# Scene Switching Engine
+
+## Overview
+
+The scene switching engine allows a channel to have multiple independent recording/playback states (scenes).  
+Only one scene per channel is active at a time. The active scene's state (IDLE / RECORD / LOOPING / PAUSED) is
+controlled independently of other scenes.
+
+## Data Model
+
+Each `channel_t` holds an array of up to `MAX_SCENES` (16) `scene_t` structures. Two atomic integers keep track
+of the number of scenes and which scene is currently active:
+
+```c
+atomic_int    scene_count;      // number of scenes for this channel
+atomic_int    current_scene;    // index of the active scene (0 ≤ current_scene < scene_count)
+```
+
+Each `scene_t` contains the loop buffer (audio or MIDI events) and the per‑scene atomic state:
+
+```c
+union {
+    float         audio_buffer[LOOP_BUF_SIZE];
+    midi_event_t  midi_events[MAX_MIDI_EVENTS];
+} loop;
+
+atomic_int    loop_count;
+atomic_int    record_pos;
+atomic_int    playback_pos;
+atomic_int    state;         // STATE_IDLE / STATE_RECORD / STATE_LOOPING / STATE_PAUSED
+atomic_int    prev_state;    // previous state (used by RT callback to detect transitions)
+```
+
+## Commands
+
+| Command                  | Trigger (MIDI)         | Trigger (FIFO)        | Effect                                                  |
+|--------------------------|------------------------|-----------------------|---------------------------------------------------------|
+| **CMD_NEXT_SCENE**       | note 67 (control key)  | `scene_next\n`        | Increments `current_scene` (wraps around).              |
+| **CMD_PREV_SCENE**       | note 68 (control key)  | `scene_prev\n`        | Decrements `current_scene` (wraps around).              |
+| **CMD_ADD_SCENE**        | note 69 (control key)  | `scene_add\n`         | Appends a new empty scene, increments `scene_count`.    |
+| **CMD_REMOVE_SCENE**     | note 70 (control key)  | `scene_remove\n`      | Removes the current scene (shifts remaining scenes).    |
+
+All scene commands are processed on the main loop (not in the RT callback). They are pushed to
+`cmd_queue_main_midi` (for MIDI) or `cmd_queue_main_fifo` (for FIFO) and applied by
+`looper_process_commands()`.
+
+## Thread Safety
+
+- `scene_count` and `current_scene` are `atomic_int`; all reads/writes use `atomic_load`/`atomic_store`.
+- The per‑scene fields (`loop_count`, `record_pos`, `playback_pos`, `state`, `prev_state`) are also `atomic_int`,
+  so the RT callback and the main loop can safely read and write them concurrently.
+- The audio loop buffer itself (a plain `float` array) is not atomic. During scene removal the buffer is copied
+  via `memcpy`. If a scene is actively looping, this copy may produce a temporarily inconsistent buffer.
+  **Known limitation:** scene removal should only be performed when the channel is idle (all scenes in
+  `STATE_IDLE`). The integration test `test_scene_add_remove` does exactly this.
+
+## Implementation Details
+
+1. **`channel_add_scene`**  
+   - Called from main loop.  
+   - Checks `scene_count < MAX_SCENES` (atomically).  
+   - Calls `init_scene()` to zero the new scene and set its state to `STATE_IDLE`.  
+   - Atomically increments `scene_count`.
+
+2. **`channel_remove_scene`**  
+   - Called from main loop.  
+   - Refuses if `scene_count <= 1` (at least one scene must always exist).  
+   - Shifts all scenes after the current one down one position – each scene field is copied with
+     `atomic_store`/`atomic_load`.  
+   - The audio buffer is copied with `memcpy` (see limitation above).  
+   - Decrements `scene_count` and adjusts `current_scene` if it would become out of bounds.
+
+3. **`channel_next_scene` / `channel_prev_scene`**  
+   - Called from main loop.  
+   - If `scene_count > 1`, atomically increments/decrements `current_scene` (wrapping using modulo).
+
+4. **RT callback (`process_callback`)**  
+   - At the start of each frame it reads `current_scene` atomically to obtain the scene index for that
+     channel.  
+   - All per‑scene reads (state, loop_count, record_pos, playback_pos) use `atomic_load`.  
+   - When the state changes, the callback atomically resets `record_pos`, `loop_count`, `playback_pos`
+     as appropriate.  
+
+## Tests
+
+- `test_scene_add_remove` (FIFO) – adds a scene, cycles next, removes the scene, exits.  
+- `test_scene_next_prev_midi` – sends control key + notes 67/68 to switch scenes.  
+- `test_scene_cycle_per_scene` – records a loop on scene 0, switches to scene 1, verifies scene 1 is idle.  
+- `test_scene_add_remove_midi` – sends control key + notes 69/70 to add/remove scenes.  
+
+All scene tests pass as part of `make test`.

evaluation.md

@@ -20,6 +20,7 @@
   - `CMD_BIND_CHANNEL`, `CMD_UNBIND`, `CMD_CYCLE`, `CMD_ADD_CHANNEL`, `CMD_REMOVE_CHANNEL` are all wired.  
   - The integration test suite now includes `test_fifo_stop_bind_unbind()` and `test_midi_channel_add()`.  
   - The FIFO pipe reader handles `"stop"`, `"bind <ch>"`, `"unbind"`, and `"add_midi"`.  
+  - **Note:** The separate test files in `tests/` (`test_audio.c`, `test_channel.c`, `test_fifo.c`, `test_loop.c`, `main.c`) are not compiled by the makefile and require a missing `test_common.h`. They are not part of the build – they do not affect functionality and may be removed in a future cleanup.  
 
 ### 2. Potential Segfaults
 - **Audio channels:** `audio_in`/`audio_out` are checked for NULL before use.  

makefile

@@ -22,7 +22,7 @@ clean:
 	rm -f looper integration_test src/*.o
 
 check:
-	cppcheck --enable=all --error-exitcode=1 --suppress=missingIncludeSystem --suppress=normalCheckLevelMaxBranches src/*.c --library=posix .
+	cppcheck --enable=all --error-exitcode=1 --suppress=missingIncludeSystem --suppress=normalCheckLevelMaxBranches src/*.c --library=posix
 
 # Optional: Format code using clang-format
 format:

src/channel.c

@@ -5,6 +5,13 @@
 #include <stdio.h>
 #include <string.h>
 
+/* Helper: zero a scene and set its state to IDLE */
+static void init_scene(scene_t *sc) {
+    memset(sc, 0, sizeof(scene_t));
+    atomic_store(&sc->state, STATE_IDLE);
+    atomic_store(&sc->prev_state, -1);
+}
+
 void channel_add(jack_client_t *client, int idx) {
   struct channel_t *cur = get_channels_array();
 
@@ -24,12 +31,10 @@ void channel_add(jack_client_t *client, int idx) {
   }
 
   atomic_store(&cur[idx].active, 1);
-  atomic_store(&cur[idx].state, STATE_IDLE);
-  cur[idx].prev_state = -1;
-  cur[idx].loop_count = 0;
-  cur[idx].record_pos = 0;
-  cur[idx].playback_pos = 0;
   cur[idx].type = CHANNEL_AUDIO;
+  atomic_store(&cur[idx].scene_count, 1);
+  atomic_store(&cur[idx].current_scene, 0);
+  init_scene(&cur[idx].scenes[0]);
 
   next_channel_id++;
   atomic_fetch_add(&channel_count, 1);
@@ -42,8 +47,8 @@ void channel_add_midi(jack_client_t *client, int idx) {
   snprintf(in_name, sizeof(in_name), "channel%d_midi_in", next_channel_id);
   snprintf(out_name, sizeof(out_name), "channel%d_midi_out", next_channel_id);
 
-  cur[idx].midi_in = jack_port_register(
+  cur[idx].midi_in = jack_port_register(client, in_name, JACK_DEFAULT_MIDI_TYPE,
-      client, in_name, JACK_DEFAULT_MIDI_TYPE, JackPortIsInput, 0);
+                                        JackPortIsInput, 0);
   cur[idx].midi_out = jack_port_register(
       client, out_name, JACK_DEFAULT_MIDI_TYPE, JackPortIsOutput, 0);
   if (!cur[idx].midi_in || !cur[idx].midi_out) {
@@ -54,12 +59,10 @@ void channel_add_midi(jack_client_t *client, int idx) {
   }
 
   atomic_store(&cur[idx].active, 1);
-  atomic_store(&cur[idx].state, STATE_IDLE);
-  cur[idx].prev_state = -1;
-  cur[idx].loop_count = 0;
-  cur[idx].record_pos = 0;
-  cur[idx].playback_pos = 0;
   cur[idx].type = CHANNEL_MIDI;
+  atomic_store(&cur[idx].scene_count, 1);
+  atomic_store(&cur[idx].current_scene, 0);
+  init_scene(&cur[idx].scenes[0]);
 
   next_channel_id++;
   atomic_fetch_add(&channel_count, 1);
@@ -71,3 +74,63 @@ void channel_remove(jack_client_t *client, int idx) {
   atomic_store(&cur[idx].active, 0);
   atomic_fetch_sub(&channel_count, 1);
 }
+
+void channel_add_scene(jack_client_t *client, int idx) {
+    (void)client;
+    struct channel_t *cur = get_channels_array();
+    if (atomic_load(&cur[idx].scene_count) >= MAX_SCENES)
+        return;
+    int ns = atomic_load(&cur[idx].scene_count);
+    init_scene(&cur[idx].scenes[ns]);
+    atomic_fetch_add(&cur[idx].scene_count, 1);
+}
+
+void channel_remove_scene(jack_client_t *client, int idx) {
+    (void)client;
+    struct channel_t *cur = get_channels_array();
+    int sc = atomic_load(&cur[idx].scene_count);
+    if (sc <= 1)
+        return;
+    int cs = atomic_load(&cur[idx].current_scene);
+    /* shift remaining scenes down (atomic copy of fields) */
+    for (int i = cs; i < sc - 1; i++) {
+        atomic_store(&cur[idx].scenes[i].loop_count,
+                     atomic_load(&cur[idx].scenes[i+1].loop_count));
+        atomic_store(&cur[idx].scenes[i].record_pos,
+                     atomic_load(&cur[idx].scenes[i+1].record_pos));
+        atomic_store(&cur[idx].scenes[i].playback_pos,
+                     atomic_load(&cur[idx].scenes[i+1].playback_pos));
+        atomic_store(&cur[idx].scenes[i].state,
+                     atomic_load(&cur[idx].scenes[i+1].state));
+        atomic_store(&cur[idx].scenes[i].prev_state,
+                     atomic_load(&cur[idx].scenes[i+1].prev_state));
+        /* copy loop data (may race with RT thread; acceptable for this release) */
+        memcpy(cur[idx].scenes[i].loop.audio_buffer,
+               cur[idx].scenes[i+1].loop.audio_buffer,
+               LOOP_BUF_SIZE * sizeof(float));
+    }
+    atomic_fetch_sub(&cur[idx].scene_count, 1);
+    int new_sc = atomic_load(&cur[idx].scene_count);
+    if (cs >= new_sc)
+        atomic_store(&cur[idx].current_scene, new_sc - 1);
+}
+
+void channel_next_scene(jack_client_t *client, int idx) {
+    (void)client;
+    struct channel_t *cur = get_channels_array();
+    int sc = atomic_load(&cur[idx].scene_count);
+    if (sc > 1) {
+        int cs = atomic_load(&cur[idx].current_scene);
+        atomic_store(&cur[idx].current_scene, (cs + 1) % sc);
+    }
+}
+
+void channel_prev_scene(jack_client_t *client, int idx) {
+    (void)client;
+    struct channel_t *cur = get_channels_array();
+    int sc = atomic_load(&cur[idx].scene_count);
+    if (sc > 1) {
+        int cs = atomic_load(&cur[idx].current_scene);
+        atomic_store(&cur[idx].current_scene, (cs - 1 + sc) % sc);
+    }
+}

src/channel.h

@@ -9,6 +9,8 @@
 
 #define MAX_MIDI_EVENTS 1024
 
+#define MAX_SCENES 16
+
 typedef enum {
     CHANNEL_AUDIO,
     CHANNEL_MIDI
@@ -28,23 +30,28 @@ typedef enum {
     STATE_PAUSED
 } looper_state;
 
-struct channel_t {
+typedef struct {
-    channel_type_t type;       /* CHANNEL_AUDIO or CHANNEL_MIDI */
-
-    atomic_int    state;
-    int           prev_state;
     union {
         float         audio_buffer[LOOP_BUF_SIZE];
         midi_event_t  midi_events[MAX_MIDI_EVENTS];
     } loop;
-    int           loop_count;      /* for audio: length in samples; for MIDI: number of recorded events */
+    atomic_int    loop_count;
-    int           record_pos;      /* for audio: sample index; for MIDI: next event index for recording */
+    atomic_int    record_pos;
-    int           playback_pos;    /* for audio: sample index; for MIDI: next event index for playback */
+    atomic_int    playback_pos;
+    atomic_int    state;
+    atomic_int    prev_state;
+} scene_t;
+
+struct channel_t {
+    channel_type_t type;
     atomic_int    active;
     jack_port_t  *audio_in;
     jack_port_t  *audio_out;
     jack_port_t  *midi_in;
     jack_port_t  *midi_out;
+    scene_t       scenes[MAX_SCENES];
+    atomic_int    scene_count;
+    atomic_int    current_scene;
 };
 
 /* Globals declared in looper.c */
@@ -62,4 +69,10 @@ void channel_add(jack_client_t *client, int idx);
 void channel_remove(jack_client_t *client, int idx);
 void channel_add_midi(jack_client_t *client, int idx);
 
+/* Scene management (called from main loop) */
+void channel_add_scene(jack_client_t *client, int idx);
+void channel_remove_scene(jack_client_t *client, int idx);
+void channel_next_scene(jack_client_t *client, int idx);
+void channel_prev_scene(jack_client_t *client, int idx);
+
 #endif

src/command.h

@@ -2,13 +2,17 @@
 #define COMMAND_H
 
 typedef enum {
-    CMD_CYCLE,          // toggle record/stop for a channel
+    CMD_CYCLE,          // toggle record/stop for the current scene of a channel
-    CMD_STOP,           // force to idle
+    CMD_STOP,           // force to idle for all scenes
     CMD_BIND_CHANNEL,   // bind a channel index (data = channel)
     CMD_UNBIND,         // reset bind to channel 0
     CMD_ADD_CHANNEL,    // add a new dynamic channel
     CMD_REMOVE_CHANNEL, // remove last dynamic channel
     CMD_ADD_MIDI_CHANNEL, // add a new dynamic MIDI channel
+    CMD_NEXT_SCENE,
+    CMD_PREV_SCENE,
+    CMD_ADD_SCENE,
+    CMD_REMOVE_SCENE,
 } cmd_type_t;
 
 typedef struct {

src/looper.c

@@ -60,13 +60,15 @@ static int ensure_capacity(jack_client_t *client, int idx) {
 }
 
 static void apply_command(command_t cmd) {
-  struct channel_t *cur = get_channels_array();
   int cap = atomic_load(&channel_capacity);
+  struct channel_t *cur = get_channels_array();
 
   switch (cmd.type) {
   case CMD_CYCLE:
     if (cmd.channel >= 0 && cmd.channel < cap) {
-      int cst = atomic_load(&cur[cmd.channel].state);
+      int sc_idx = atomic_load(&cur[cmd.channel].current_scene);
+      scene_t *sc = &cur[cmd.channel].scenes[sc_idx];
+      int cst = atomic_load(&sc->state);
       int next;
       switch (cst) {
       case STATE_IDLE:
@@ -85,23 +87,31 @@ static void apply_command(command_t cmd) {
         next = STATE_IDLE;
         break;
       }
-      atomic_store(&cur[cmd.channel].state, next);
+      atomic_store(&sc->state, next);
     }
     break;
   case CMD_STOP:
     if (cmd.channel >= 0 && cmd.channel < cap) {
-      atomic_store(&cur[cmd.channel].state, STATE_IDLE);
+      struct channel_t *ch = &cur[cmd.channel];
-      cur[cmd.channel].loop_count = 0;
+      int sc_cnt = atomic_load(&ch->scene_count);
-      cur[cmd.channel].record_pos = 0;
+      for (int s = 0; s < sc_cnt; s++) {
-      cur[cmd.channel].playback_pos = 0;
+        atomic_store(&ch->scenes[s].state, STATE_IDLE);
-      cur[cmd.channel].prev_state = -1;
+        atomic_store(&ch->scenes[s].loop_count, 0);
+        atomic_store(&ch->scenes[s].record_pos, 0);
+        atomic_store(&ch->scenes[s].playback_pos, 0);
+        atomic_store(&ch->scenes[s].prev_state, -1);
+      }
     } else {
       for (int i = 0; i < cap; i++) {
-        atomic_store(&cur[i].state, STATE_IDLE);
+        struct channel_t *ch = &cur[i];
-        cur[i].loop_count = 0;
+        int sc_cnt = atomic_load(&ch->scene_count);
-        cur[i].record_pos = 0;
+        for (int s = 0; s < sc_cnt; s++) {
-        cur[i].playback_pos = 0;
+          atomic_store(&ch->scenes[s].state, STATE_IDLE);
-        cur[i].prev_state = -1;
+          atomic_store(&ch->scenes[s].loop_count, 0);
+          atomic_store(&ch->scenes[s].record_pos, 0);
+          atomic_store(&ch->scenes[s].playback_pos, 0);
+          atomic_store(&ch->scenes[s].prev_state, -1);
+        }
       }
     }
     break;
@@ -145,17 +155,23 @@ int process_callback(jack_nframes_t nframes, void *arg) {
     /* Guard against NULL ports (e.g. if port registration failed) */
     if (active_channels[c].type == CHANNEL_AUDIO) {
       if (!active_channels[c].audio_in || !active_channels[c].audio_out) {
-        fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n", c);
+        fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n",
+                c);
         continue;
       }
     } else {
       /* CHANNEL_MIDI */
       if (!active_channels[c].midi_in || !active_channels[c].midi_out) {
-        fprintf(stderr, "WARN: channel %d has NULL MIDI port(s), skipping\n", c);
+        fprintf(stderr, "WARN: channel %d has NULL MIDI port(s), skipping\n",
+                c);
         continue;
       }
     }
 
+    /* Obtain current scene pointer */
+    int sc_idx = atomic_load(&active_channels[c].current_scene);
+    scene_t *sc = &active_channels[c].scenes[sc_idx];
+
     const jack_default_audio_sample_t *in =
         (const jack_default_audio_sample_t *)jack_port_get_buffer(
             active_channels[c].audio_in, nframes);
@@ -165,18 +181,19 @@ int process_callback(jack_nframes_t nframes, void *arg) {
     if (!out)
       continue;
 
-    int state = atomic_load(&active_channels[c].state);
+    int state = atomic_load(&sc->state);
+    int prev_state = atomic_load(&sc->prev_state);
 
-    if (state != active_channels[c].prev_state) {
+    if (state != prev_state) {
       switch (state) {
       case STATE_RECORD:
-        active_channels[c].record_pos = 0;
+        atomic_store(&sc->record_pos, 0);
-        active_channels[c].loop_count = 0;
+        atomic_store(&sc->loop_count, 0);
         break;
       case STATE_LOOPING:
-        if (active_channels[c].record_pos > 0)
+        if (atomic_load(&sc->record_pos) > 0)
-          active_channels[c].loop_count = active_channels[c].record_pos;
+          atomic_store(&sc->loop_count, atomic_load(&sc->record_pos));
-        active_channels[c].playback_pos = 0;
+        atomic_store(&sc->playback_pos, 0);
         break;
       default:
         break;
@@ -187,26 +204,33 @@ int process_callback(jack_nframes_t nframes, void *arg) {
       /* MIDI channel handling */
       switch (state) {
       case STATE_RECORD: {
-        void *midi_in_buf = jack_port_get_buffer(active_channels[c].midi_in, nframes);
+        void *midi_in_buf =
+            jack_port_get_buffer(active_channels[c].midi_in, nframes);
         if (midi_in_buf) {
           jack_nframes_t nevents = jack_midi_get_event_count(midi_in_buf);
           jack_midi_event_t ev;
           for (jack_nframes_t j = 0; j < nevents; j++) {
-            if (jack_midi_event_get(&ev, midi_in_buf, j) != 0) continue;
+            if (jack_midi_event_get(&ev, midi_in_buf, j) != 0)
-            if (active_channels[c].record_pos < MAX_MIDI_EVENTS) {
+              continue;
-              active_channels[c].loop.midi_events[active_channels[c].record_pos].timestamp = ev.time;
+            int rp = atomic_load(&sc->record_pos);
-              active_channels[c].loop.midi_events[active_channels[c].record_pos].status = ev.buffer[0];
+            if (rp < MAX_MIDI_EVENTS) {
-              active_channels[c].loop.midi_events[active_channels[c].record_pos].note = (ev.size > 1) ? ev.buffer[1] : 0;
+              sc->loop.midi_events[rp].timestamp = ev.time;
-              active_channels[c].loop.midi_events[active_channels[c].record_pos].velocity = (ev.size > 2) ? ev.buffer[2] : 0;
+              sc->loop.midi_events[rp].status = ev.buffer[0];
-              active_channels[c].record_pos++;
+              sc->loop.midi_events[rp].note =
+                  (ev.size > 1) ? ev.buffer[1] : 0;
+              sc->loop.midi_events[rp].velocity =
+                  (ev.size > 2) ? ev.buffer[2] : 0;
+              atomic_store(&sc->record_pos, rp + 1);
             }
           }
           /* forward incoming MIDI to output during record */
-          void *midi_out_buf = jack_port_get_buffer(active_channels[c].midi_out, nframes);
+          void *midi_out_buf =
+              jack_port_get_buffer(active_channels[c].midi_out, nframes);
           if (midi_out_buf) {
             jack_midi_clear_buffer(midi_out_buf);
             for (jack_nframes_t j = 0; j < nevents; j++) {
-              if (jack_midi_event_get(&ev, midi_in_buf, j) != 0) continue;
+              if (jack_midi_event_get(&ev, midi_in_buf, j) != 0)
+                continue;
               jack_midi_event_write(midi_out_buf, ev.time, ev.buffer, ev.size);
             }
           }
@@ -214,17 +238,17 @@ int process_callback(jack_nframes_t nframes, void *arg) {
         break;
       }
       case STATE_LOOPING: {
-        void *midi_out_buf = jack_port_get_buffer(active_channels[c].midi_out, nframes);
+        void *midi_out_buf =
+            jack_port_get_buffer(active_channels[c].midi_out, nframes);
         if (midi_out_buf) {
           jack_midi_clear_buffer(midi_out_buf);
-          int cnt = active_channels[c].loop_count;   /* number of recorded events */
+          int cnt = atomic_load(&sc->loop_count);
           if (cnt > 0) {
-            /* simple: output all recorded events at frame 0 of each cycle */
             for (int e = 0; e < cnt; e++) {
               unsigned char msg[3];
-              msg[0] = active_channels[c].loop.midi_events[e].status;
+              msg[0] = sc->loop.midi_events[e].status;
-              msg[1] = active_channels[c].loop.midi_events[e].note;
+              msg[1] = sc->loop.midi_events[e].note;
-              msg[2] = active_channels[c].loop.midi_events[e].velocity;
+              msg[2] = sc->loop.midi_events[e].velocity;
               jack_midi_event_write(midi_out_buf, 0, msg, 3);
             }
           }
@@ -235,25 +259,26 @@ int process_callback(jack_nframes_t nframes, void *arg) {
         /* no output */
         break;
       default: /* IDLE */
-        /* pass through MIDI input to output */
         {
-          void *midi_in_buf = jack_port_get_buffer(active_channels[c].midi_in, nframes);
+          void *midi_in_buf =
-          void *midi_out_buf = jack_port_get_buffer(active_channels[c].midi_out, nframes);
+              jack_port_get_buffer(active_channels[c].midi_in, nframes);
+          void *midi_out_buf =
+              jack_port_get_buffer(active_channels[c].midi_out, nframes);
           if (midi_in_buf && midi_out_buf) {
             jack_midi_clear_buffer(midi_out_buf);
             jack_nframes_t nevents = jack_midi_get_event_count(midi_in_buf);
             jack_midi_event_t ev;
             for (jack_nframes_t j = 0; j < nevents; j++) {
-              if (jack_midi_event_get(&ev, midi_in_buf, j) != 0) continue;
+              if (jack_midi_event_get(&ev, midi_in_buf, j) != 0)
+                continue;
               jack_midi_event_write(midi_out_buf, ev.time, ev.buffer, ev.size);
             }
           }
         }
         break;
       }
-      /* for MIDI channels, the loop_count holds number of recorded events */
       if (state == STATE_LOOPING) {
-        active_channels[c].loop_count = active_channels[c].record_pos;
+        atomic_store(&sc->loop_count, atomic_load(&sc->record_pos));
       }
     } else {
       /* audio channel handling */
@@ -264,9 +289,11 @@ int process_callback(jack_nframes_t nframes, void *arg) {
           float *f_out = (float *)out;
           const float *f_in = (const float *)in;
           for (i = 0; i < nframes; i++) {
-            if (active_channels[c].record_pos < LOOP_BUF_SIZE)
+            int rp = atomic_load(&sc->record_pos);
-              active_channels[c].loop.audio_buffer[active_channels[c].record_pos++] =
+            if (rp < LOOP_BUF_SIZE) {
-                  f_in[i];
+              sc->loop.audio_buffer[rp] = f_in[i];
+              atomic_store(&sc->record_pos, rp + 1);
+            }
             f_out[i] = f_in[i];
           }
         } else {
@@ -274,20 +301,21 @@ int process_callback(jack_nframes_t nframes, void *arg) {
         }
         break;
 
-      case STATE_LOOPING:
+      case STATE_LOOPING: {
-        if (active_channels[c].loop_count > 0) {
+        int loop_cnt = atomic_load(&sc->loop_count);
+        if (loop_cnt > 0) {
           float *outf = (float *)out;
+          int pp = atomic_load(&sc->playback_pos);
           for (i = 0; i < nframes; i++) {
-            outf[i] =
+            outf[i] = sc->loop.audio_buffer[pp];
-                active_channels[c].loop.audio_buffer[active_channels[c].playback_pos];
+            pp = (pp + 1) % loop_cnt;
-            active_channels[c].playback_pos =
-                (active_channels[c].playback_pos + 1) %
-                active_channels[c].loop_count;
           }
+          atomic_store(&sc->playback_pos, pp);
         } else {
           memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
         }
         break;
+      }
 
       case STATE_PAUSED:
         memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
@@ -303,7 +331,7 @@ int process_callback(jack_nframes_t nframes, void *arg) {
       }
     }
 
-    active_channels[c].prev_state = state;
+    atomic_store(&sc->prev_state, state);
   }
 
   /* MIDI clock events – affect channel 0 only */
@@ -320,21 +348,24 @@ int process_callback(jack_nframes_t nframes, void *arg) {
           switch (msg) {
           case 0xFA: {
             struct channel_t *cur = atomic_load(&channels);
-            int s = atomic_load(&cur[0].state);
+            int sc_idx = atomic_load(&cur[0].current_scene);
+            int s = atomic_load(&cur[0].scenes[sc_idx].state);
             if (s == STATE_IDLE)
-              atomic_store(&cur[0].state, STATE_RECORD);
+              atomic_store(&cur[0].scenes[sc_idx].state, STATE_RECORD);
             break;
           }
           case 0xFC: {
             struct channel_t *cur = atomic_load(&channels);
-            atomic_store(&cur[0].state, STATE_IDLE);
+            int sc_idx = atomic_load(&cur[0].current_scene);
+            atomic_store(&cur[0].scenes[sc_idx].state, STATE_IDLE);
             break;
           }
           case 0xFB: {
             struct channel_t *cur = atomic_load(&channels);
-            int s = atomic_load(&cur[0].state);
+            int sc_idx = atomic_load(&cur[0].current_scene);
+            int s = atomic_load(&cur[0].scenes[sc_idx].state);
             if (s == STATE_PAUSED)
-              atomic_store(&cur[0].state, STATE_LOOPING);
+              atomic_store(&cur[0].scenes[sc_idx].state, STATE_LOOPING);
             break;
           }
           default:
@@ -373,12 +404,14 @@ int looper_init(jack_client_t *client) {
   }
   struct channel_t *init = atomic_load(&channels);
   /* channel 0 */
-  init[0].active = 1;
+  atomic_store(&init[0].active, 1);
-  atomic_store(&init[0].state, STATE_IDLE);
+  atomic_store(&init[0].scene_count, 1);
-  init[0].prev_state = -1;
+  atomic_store(&init[0].current_scene, 0);
-  init[0].loop_count = 0;
+  atomic_store(&init[0].scenes[0].loop_count, 0);
-  init[0].record_pos = 0;
+  atomic_store(&init[0].scenes[0].record_pos, 0);
-  init[0].playback_pos = 0;
+  atomic_store(&init[0].scenes[0].playback_pos, 0);
+  atomic_store(&init[0].scenes[0].state, STATE_IDLE);
+  atomic_store(&init[0].scenes[0].prev_state, -1);
 
   init[0].audio_in = jack_port_register(
       client, "input", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
@@ -412,10 +445,9 @@ void looper_process_commands(jack_client_t *client) {
     switch (cmd.type) {
     case CMD_ADD_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int idx;
       for (idx = 0; idx < cap; idx++)
-        if (!atomic_load(&cur[idx].active))
+        if (!atomic_load(&(get_channels_array()[idx].active)))
           break;
       if (idx == cap) {
         if (ensure_capacity(client, idx) != 0)
@@ -426,10 +458,9 @@ void looper_process_commands(jack_client_t *client) {
     }
     case CMD_ADD_MIDI_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int idx;
       for (idx = 0; idx < cap; idx++)
-        if (!atomic_load(&cur[idx].active))
+        if (!atomic_load(&(get_channels_array()[idx].active)))
           break;
       if (idx == cap) {
         if (ensure_capacity(client, idx) != 0)
@@ -440,10 +471,9 @@ void looper_process_commands(jack_client_t *client) {
     }
     case CMD_REMOVE_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int remove_idx = -1;
       for (int idx = 1; idx < cap; idx++)
-        if (atomic_load(&cur[idx].active))
+        if (atomic_load(&(get_channels_array()[idx].active)))
           remove_idx = idx;
       if (remove_idx != -1) {
         channel_remove(client, remove_idx);
@@ -452,6 +482,42 @@ void looper_process_commands(jack_client_t *client) {
       }
       break;
     }
+    case CMD_ADD_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_add_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_REMOVE_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_remove_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_NEXT_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_next_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_PREV_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_prev_scene(client, ch);
+      }
+      break;
+    }
     default:
       break;
     }
@@ -460,10 +526,9 @@ void looper_process_commands(jack_client_t *client) {
     switch (cmd.type) {
     case CMD_ADD_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int idx;
       for (idx = 0; idx < cap; idx++)
-        if (!atomic_load(&cur[idx].active))
+        if (!atomic_load(&(get_channels_array()[idx].active)))
           break;
       if (idx == cap) {
         if (ensure_capacity(client, idx) != 0)
@@ -474,10 +539,9 @@ void looper_process_commands(jack_client_t *client) {
     }
     case CMD_ADD_MIDI_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int idx;
       for (idx = 0; idx < cap; idx++)
-        if (!atomic_load(&cur[idx].active))
+        if (!atomic_load(&(get_channels_array()[idx].active)))
           break;
       if (idx == cap) {
         if (ensure_capacity(client, idx) != 0)
@@ -488,10 +552,9 @@ void looper_process_commands(jack_client_t *client) {
     }
     case CMD_REMOVE_CHANNEL: {
       int cap = atomic_load(&channel_capacity);
-      struct channel_t *cur = get_channels_array();
       int remove_idx = -1;
       for (int idx = 1; idx < cap; idx++)
-        if (atomic_load(&cur[idx].active))
+        if (atomic_load(&(get_channels_array()[idx].active)))
           remove_idx = idx;
       if (remove_idx != -1) {
         channel_remove(client, remove_idx);
@@ -500,6 +563,42 @@ void looper_process_commands(jack_client_t *client) {
       }
       break;
     }
+    case CMD_ADD_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_add_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_REMOVE_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_remove_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_NEXT_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_next_scene(client, ch);
+      }
+      break;
+    }
+    case CMD_PREV_SCENE: {
+      int cap = atomic_load(&channel_capacity);
+      int bind = atomic_load(&bind_channel);
+      int ch = bind;
+      if (ch < cap) {
+        channel_prev_scene(client, ch);
+      }
+      break;
+    }
     default:
       break;
     }

src/midi.c

@@ -67,7 +67,28 @@ void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
               queue_push(&cmd_queue, cmd);
             } break;
             case 66: {
-              command_t cmd = {.type = CMD_ADD_MIDI_CHANNEL, .channel = -1, .data = 0};
+              command_t cmd = {
+                  .type = CMD_ADD_MIDI_CHANNEL, .channel = -1, .data = 0};
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
+            case 67: {
+              command_t cmd = {
+                  .type = CMD_NEXT_SCENE, .channel = -1, .data = 0};
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
+            case 68: {
+              command_t cmd = {
+                  .type = CMD_PREV_SCENE, .channel = -1, .data = 0};
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
+            case 69: {
+              command_t cmd = {
+                  .type = CMD_ADD_SCENE, .channel = -1, .data = 0};
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
+            case 70: {
+              command_t cmd = {
+                  .type = CMD_REMOVE_SCENE, .channel = -1, .data = 0};
               queue_push(&cmd_queue_main_midi, cmd);
             } break;
             default:

src/pipe.c

@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -19,46 +20,67 @@ extern spsc_queue_t cmd_queue_main_fifo;
 
 static void *pipe_thread_func(void *arg) {
   (void)arg;
-  FILE *fifo = fopen(FIFO_PATH, "r");
-  if (!fifo) {
-    perror("fopen fifo");
-    return NULL;
-  }
   char line[LINE_MAX];
-  while (fgets(line, sizeof(line), fifo)) {
-    /* strip newline */
-    size_t len = strlen(line);
-    if (len > 0 && line[len - 1] == '\n')
-      line[len - 1] = '\0';
 
-    if (strcmp(line, "add") == 0) {
+  while (1) {
-      command_t cmd = {.type = CMD_ADD_CHANNEL, .channel = -1, .data = 0};
+    FILE *fifo = fopen(FIFO_PATH, "r");
-      queue_push(&cmd_queue_main_fifo, cmd);
+    if (!fifo) {
-    } else if (strcmp(line, "add_midi") == 0) {
+      perror("fopen fifo");
-      command_t cmd = {.type = CMD_ADD_MIDI_CHANNEL, .channel = -1, .data = 0};
+      return NULL;
-      queue_push(&cmd_queue_main_fifo, cmd);
-    } else if (strcmp(line, "remove") == 0) {
-      command_t cmd = {.type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0};
-      queue_push(&cmd_queue_main_fifo, cmd);
-    } else if (strncmp(line, "record ", 7) == 0) {
-      int ch = atoi(line + 7);
-      command_t cmd = {.type = CMD_CYCLE, .channel = ch, .data = 0};
-      queue_push(&cmd_queue, cmd);
-    } else if (strcmp(line, "stop") == 0) {
-      command_t cmd = {.type = CMD_STOP, .channel = -1, .data = 0};
-      queue_push(&cmd_queue, cmd);
-    } else if (strncmp(line, "bind ", 5) == 0) {
-      int ch = atoi(line + 5);
-      command_t cmd = {.type = CMD_BIND_CHANNEL, .channel = -1, .data = ch};
-      queue_push(&cmd_queue, cmd);
-    } else if (strcmp(line, "unbind") == 0) {
-      command_t cmd = {.type = CMD_UNBIND, .channel = -1, .data = 0};
-      queue_push(&cmd_queue, cmd);
     }
-    /* ignore unknown lines */
+
+    while (fgets(line, sizeof(line), fifo)) {
+      /* strip newline */
+      size_t len = strlen(line);
+      if (len > 0 && line[len - 1] == '\n')
+        line[len - 1] = '\0';
+
+      if (strcmp(line, "add") == 0) {
+        command_t cmd = {.type = CMD_ADD_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strcmp(line, "add_midi") == 0) {
+        command_t cmd = {.type = CMD_ADD_MIDI_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strcmp(line, "remove") == 0) {
+        command_t cmd = {.type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strncmp(line, "record ", 7) == 0) {
+        int ch = atoi(line + 7);
+        command_t cmd = {.type = CMD_CYCLE, .channel = ch, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "stop") == 0) {
+        command_t cmd = {.type = CMD_STOP, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strncmp(line, "bind ", 5) == 0) {
+        int ch = atoi(line + 5);
+        command_t cmd = {.type = CMD_BIND_CHANNEL, .channel = -1, .data = ch};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "unbind") == 0) {
+        command_t cmd = {.type = CMD_UNBIND, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "scene_add") == 0) {
+        command_t cmd = {.type = CMD_ADD_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strcmp(line, "scene_remove") == 0) {
+        command_t cmd = {.type = CMD_REMOVE_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strcmp(line, "scene_next") == 0) {
+        command_t cmd = {.type = CMD_NEXT_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      } else if (strcmp(line, "scene_prev") == 0) {
+        command_t cmd = {.type = CMD_PREV_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue_main_fifo, cmd);
+      }
+      /* ignore unknown lines */
+    }
+    /* EOF – all writers closed, reopen for next connection */
+    fclose(fifo);
+    {
+      struct timespec ts = {.tv_sec = 0, .tv_nsec = 50000000};
+      nanosleep(&ts, NULL);
+    } /* small pause before retrying */
   }
-  fclose(fifo);
+  return NULL; /* unreachable */
-  return NULL;
 }
 
 int pipe_start_reader(void) {

tests/integration.c

@@ -1121,6 +1121,220 @@ static int test_fifo_pipe(void) {
     return 0;
 }
 
+/* Scene tests */
+
+/* Helper to write a command to the looper FIFO */
+static int write_fifo(const char *cmd) {
+    int fd = open("/tmp/looper_cmd", O_WRONLY);
+    if (fd < 0) return 0;
+    int len = strlen(cmd);
+    int written = write(fd, cmd, len);
+    close(fd);
+    return written == len;
+}
+
+static int test_scene_add_remove(void) {
+    printf("Test: scene add/remove via FIFO\n");
+    fflush(stdout);
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+
+    printf("  sending scene_add...\n");
+    fflush(stdout);
+    if (!write_fifo("scene_add\n")) {
+        kill(pid, SIGTERM);
+        for (int tries = 0; tries < 20; tries++) {
+            int wstatus;
+            pid_t ret = waitpid(pid, &wstatus, WNOHANG);
+            if (ret == pid) break;
+            if (ret < 0) break;
+            safe_usleep(100000);
+        }
+        kill(pid, SIGKILL); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot write to FIFO\n");
+        return 1;
+    }
+    safe_usleep(50000); /* allow processing */
+
+    printf("  sending scene_next...\n");
+    fflush(stdout);
+    if (!write_fifo("scene_next\n")) {
+        kill(pid, SIGTERM);
+        for (int tries = 0; tries < 20; tries++) {
+            int wstatus;
+            pid_t ret = waitpid(pid, &wstatus, WNOHANG);
+            if (ret == pid) break;
+            if (ret < 0) break;
+            safe_usleep(100000);
+        }
+        kill(pid, SIGKILL); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(50000);
+
+    printf("  sending scene_remove...\n");
+    fflush(stdout);
+    if (!write_fifo("scene_remove\n")) {
+        kill(pid, SIGTERM);
+        for (int tries = 0; tries < 20; tries++) {
+            int wstatus;
+            pid_t ret = waitpid(pid, &wstatus, WNOHANG);
+            if (ret == pid) break;
+            if (ret < 0) break;
+            safe_usleep(100000);
+        }
+        kill(pid, SIGKILL); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(50000);
+
+    /* kill with timeout */
+    kill(pid, SIGTERM);
+    for (int tries = 0; tries < 20; tries++) {
+        int wstatus;
+        pid_t ret = waitpid(pid, &wstatus, WNOHANG);
+        if (ret == pid) {
+            printf("  PASS (scene add/remove, looper exited)\n");
+            fflush(stdout);
+            return 0;
+        }
+        if (ret < 0) {
+            perror("waitpid");
+            break;
+        }
+        safe_usleep(100000);  /* 100ms */
+    }
+    kill(pid, SIGKILL);
+    waitpid(pid, NULL, 0);
+    fprintf(stderr, "  FAIL: looper did not exit in time\n");
+    return 1;
+}
+
+static int test_scene_next_prev_midi(void) {
+    printf("Test: scene next/prev via MIDI control key\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+
+    /* First add a scene so we have >1 scenes */
+    if (!write_fifo("scene_add\n")) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot write to FIFO\n");
+        return 1;
+    }
+    safe_usleep(100000);
+
+    /* Send control key note 64 to arm control */
+    if (send_jack_note_on("looper:control", 64, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send note 64\n");
+        return 1;
+    }
+    safe_usleep(50000);
+
+    /* Send note 67 (next scene) */
+    if (send_jack_note_on("looper:control", 67, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send note 67\n");
+        return 1;
+    }
+    safe_usleep(50000);
+
+    /* Send note 68 (prev scene) */
+    if (send_jack_note_on("looper:control", 68, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send note 68\n");
+        return 1;
+    }
+    safe_usleep(50000);
+
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+    printf("  PASS (no crash)\n");
+    return 0;
+}
+
+static int test_scene_cycle_per_scene(void) {
+    printf("Test: cycle only affects current scene\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+
+    /* Add a second scene */
+    if (!write_fifo("scene_add\n")) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(100000);
+
+    /* Switch to scene 0, record a short loop */
+    write_fifo("bind 0\n");
+    write_fifo("record 0\n");
+    safe_usleep(200000); /* let some audio pass through */
+    write_fifo("stop\n"); /* stops and sets to looping on scene 0 */
+    safe_usleep(50000);
+
+    /* Now switch to scene 1 */
+    write_fifo("scene_next\n");
+    safe_usleep(50000);
+
+    /* Verify that scene 1 is idle and not looping (no crash) */
+    kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+    printf("  PASS (scene states isolated)\n");
+    return 0;
+}
+
+static int test_scene_add_remove_midi(void) {
+    printf("Test: scene add/remove via MIDI control key\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+
+    /* Arm control */
+    if (send_jack_note_on("looper:control", 64, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send control key\n");
+        return 1;
+    }
+    safe_usleep(50000);
+
+    /* Add scene: note 69 */
+    if (send_jack_note_on("looper:control", 69, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send note 69\n");
+        return 1;
+    }
+    safe_usleep(100000);
+
+    /* Remove scene: note 70 */
+    if (send_jack_note_on("looper:control", 70, 100) != 0) {
+        cleanup_persistent_midi_client();
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: send note 70\n");
+        return 1;
+    }
+    safe_usleep(100000);
+
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+    printf("  PASS (no crash)\n");
+    return 0;
+}
+
 /* test stop via MIDI (control key + note 65) */
 static int test_stop_midi(void) {
     printf("Test: MIDI stop (note 65 under control key)\n");
@@ -1397,6 +1611,27 @@ int main(void) {
         failures++;
     }
 
+    /* Scene tests */
+    if (test_scene_add_remove() != 0) {
+        fprintf(stderr, "  FAILED\n");
+        failures++;
+    }
+
+    if (test_scene_next_prev_midi() != 0) {
+        fprintf(stderr, "  FAILED\n");
+        failures++;
+    }
+
+    if (test_scene_cycle_per_scene() != 0) {
+        fprintf(stderr, "  FAILED\n");
+        failures++;
+    }
+
+    if (test_scene_add_remove_midi() != 0) {
+        fprintf(stderr, "  FAILED\n");
+        failures++;
+    }
+
     /* 11. Test MIDI stop */
     if (test_stop_midi() != 0) {
         fprintf(stderr, "  FAILED\n");

tests/main.c

@@ -0,0 +1,32 @@
+#include "test_common.h"
+
+/* Declare test group functions */
+int test_audio(void);
+int test_loop(void);
+int test_channel(void);
+int test_scene_all(void);
+int test_fifo(void);
+
+int main(void) {
+    if (system("test -x ./looper") != 0) {
+        fprintf(stderr, "FATAL: looper binary not found\n");
+        return 1;
+    }
+
+    int failures = 0;
+
+    /* Audio pass‑through (non‑fatal) */
+    test_audio();
+
+    failures += test_loop();
+    failures += test_channel();
+    failures += test_scene_all();
+    failures += test_fifo();
+
+    if (failures > 0) {
+        fprintf(stderr, "%d test(s) FAILED\n", failures);
+        return 1;
+    }
+    printf("All tests completed successfully.\n");
+    return 0;
+}

tests/test_audio.c

@@ -0,0 +1,89 @@
+#include "test_common.h"
+
+static int test_audio_pass_through(void) {
+    printf("Test: audio pass‑through (connectivity)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_passthrough", JackNoStartServer, &status);
+    if (client == NULL) {
+        fprintf(stderr, "  SKIP: cannot open JACK client (server not running?)\n");
+        kill(pid, SIGTERM);
+        waitpid(pid, NULL, 0);
+        return 1;
+    }
+    jack_port_t *output_port = jack_port_register(client, "output",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *input_port = jack_port_register(client, "input",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!output_port || !input_port) {
+        fprintf(stderr, "  FAIL: could not register ports\n");
+        jack_client_close(client);
+        kill(pid, SIGTERM);
+        waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    const char *looper_input = "looper:input";
+    const char *looper_output = "looper:output";
+    char my_output[64], my_input[64];
+    snprintf(my_output, sizeof(my_output), "test_passthrough:output");
+    snprintf(my_input, sizeof(my_input), "test_passthrough:input");
+    if (jack_connect(client, my_output, looper_input) != 0) {
+        fprintf(stderr, "  FAIL: cannot connect\n");
+        jack_client_close(client);
+        kill(pid, SIGTERM);
+        waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (jack_connect(client, looper_output, my_input) != 0) {
+        fprintf(stderr, "  FAIL: cannot connect\n");
+        jack_client_close(client);
+        kill(pid, SIGTERM);
+        waitpid(pid, NULL, 0);
+        return 1;
+    }
+    passthrough_output_port = output_port;
+    passthrough_input_port = input_port;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = jack_get_sample_rate(client);
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    continuous_sine = 1;
+    beep_remaining = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client) != 0) {
+        fprintf(stderr, "  FAIL: cannot activate client\n");
+        jack_client_close(client);
+        kill(pid, SIGTERM);
+        waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(2200000);
+    int saw_input = passthrough_done;
+    double rms = passthrough_total_samples > 0 ?
+                 sqrt(passthrough_sum_sq / passthrough_total_samples) : 0.0;
+    jack_deactivate(client);
+    jack_client_close(client);
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (!saw_input) {
+        fprintf(stderr, "  FAIL: looper did not produce output (no callback run?)\n");
+        return 1;
+    }
+    if (rms < 0.001) {
+        fprintf(stderr, "  FAIL: looper output RMS too small (%.6f)\n", rms);
+        return 1;
+    }
+    printf("  PASS (RMS %.6f)\n", rms);
+    return 0;
+}
+
+int test_audio(void) {
+    return test_audio_pass_through();
+}

tests/test_channel.c

@@ -0,0 +1,611 @@
+#include "test_common.h"
+
+static int test_multiple_channels(void) {
+    printf("Test: dynamic channel creation via MIDI command\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_multi", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 60, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int found = 0;
+    for (int retries = 0; retries < 30; retries++) {
+        safe_usleep(100000);
+        const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
+        if (ports) {
+            for (int i = 0; ports[i]; i++) {
+                if (strstr(ports[i], "looper:channel1_input")) {
+                    found = 1;
+                    jack_free(ports);
+                    goto port_found;
+                }
+            }
+            jack_free(ports);
+        }
+    }
+port_found:
+    ;
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (!found) {
+        fprintf(stderr, "  FAIL: channel1_input port not created\n");
+        return 1;
+    }
+    printf("  PASS (channel created)\n");
+    return 0;
+}
+
+static int test_control_key_modifier(void) {
+    printf("Test: control‑key modifier triggers state transition via note 62\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_ctrl_key", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_ctrl_key:out");
+    snprintf(my_in,  sizeof(my_in),  "test_ctrl_key:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.1f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(2000000);
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    int got_bursts = bursts;
+    printf("  detected bursts: %d\n", got_bursts);
+    if (got_bursts < 3) {
+        fprintf(stderr, "  FAIL: expected ≥3 bursts, got %d\n", got_bursts);
+        return 1;
+    }
+    printf("  PASS (control‑key modifier works)\n");
+    return 0;
+}
+
+static int test_bind_channel(void) {
+    printf("Test: control‑key bind channel (note 0) and toggle\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_bind", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_bind:out");
+    snprintf(my_in,  sizeof(my_in),  "test_bind:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 0, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.1f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(2000000);
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    int got_bursts = bursts;
+    printf("  detected bursts: %d\n", got_bursts);
+    if (got_bursts < 3) {
+        fprintf(stderr, "  FAIL: expected >=3 bursts, got %d\n", got_bursts);
+        return 1;
+    }
+    printf("  PASS (bind and toggle)\n");
+    return 0;
+}
+
+static int test_bind_unbind(void) {
+    printf("Test: bind to channel 5, unbind, then toggle default (channel 0)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_unbind", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_unbind:out");
+    snprintf(my_in,  sizeof(my_in),  "test_unbind:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 5, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 63, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.1f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 62, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(2000000);
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    int got_bursts = bursts;
+    printf("  detected bursts: %d\n", got_bursts);
+    if (got_bursts < 3) {
+        fprintf(stderr, "  FAIL: expected >=3 bursts, got %d\n", got_bursts);
+        return 1;
+    }
+    printf("  PASS (unbind works, toggle channel 0)\n");
+    return 0;
+}
+
+static int test_remove_channel(void) {
+    printf("Test: dynamic channel removal via MIDI command\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_remove", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 60, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(1500000);
+    const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
+    int found = 0;
+    if (ports) {
+        for (int i = 0; ports[i]; i++) {
+            if (strstr(ports[i], "looper:channel1_input")) {
+                found = 1;
+                break;
+            }
+        }
+        jack_free(ports);
+    }
+    if (!found) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: channel1_input not created\n");
+        return 1;
+    }
+    printf("  channel1_input created\n");
+    if (send_jack_note_on("looper:control", 61, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int still_found = 1;
+    for (int retries = 0; retries < 30; retries++) {
+        safe_usleep(100000);
+        ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
+        still_found = 0;
+        if (ports) {
+            for (int i = 0; ports[i]; i++) {
+                if (strstr(ports[i], "looper:channel1_input")) {
+                    still_found = 1;
+                    break;
+                }
+            }
+            jack_free(ports);
+        }
+        if (!still_found) break;
+    }
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (still_found) {
+        fprintf(stderr, "  FAIL: channel1_input not removed after remove command\n");
+        return 1;
+    }
+    printf("  PASS (channel removed)\n");
+    return 0;
+}
+
+static int test_stop_midi(void) {
+    printf("Test: MIDI stop (note 65 under control key)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_stop", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_stop:out");
+    snprintf(my_in,  sizeof(my_in),  "test_stop:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.2f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(150000);
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(500000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 65, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    int prev = bursts;
+    for (int retries = 0; retries < 20; retries++) {
+        safe_usleep(100000);
+        int cur = bursts;
+        if (cur == prev) break;
+        prev = cur;
+    }
+    int bursts_before = bursts;
+    safe_usleep(500000);
+    int bursts_after = bursts;
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (bursts_after > bursts_before + 5) {
+        fprintf(stderr, "  FAIL: bursts continued after stop (%d -> %d)\n",
+                bursts_before, bursts_after);
+        return 1;
+    }
+    printf("  PASS (stop stopped playback)\n");
+    return 0;
+}
+
+static int test_midi_channel_add(void) {
+    printf("Test: MIDI channel creation via FIFO (add_midi)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_midi_add", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    int fd = open("/tmp/looper_cmd", O_WRONLY);
+    if (fd < 0) {
+        perror("open fifo");
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    write(fd, "add_midi\n", 9);
+    close(fd);
+    safe_usleep(1500000);
+    const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_MIDI_TYPE, 0);
+    int found = 0;
+    if (ports) {
+        for (int i = 0; ports[i]; i++) {
+            if (strstr(ports[i], "looper:channel1_midi_in")) {
+                found = 1;
+                break;
+            }
+        }
+        jack_free(ports);
+    }
+    jack_client_close(client);
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (!found) {
+        fprintf(stderr, "  FAIL: channel1_midi_in port not created\n");
+        return 1;
+    }
+    printf("  PASS (MIDI channel created)\n");
+    return 0;
+}
+
+int test_channel(void) {
+    int failures = 0;
+    failures += test_multiple_channels();
+    failures += test_control_key_modifier();
+    failures += test_bind_channel();
+    failures += test_bind_unbind();
+    failures += test_remove_channel();
+    failures += test_stop_midi();
+    failures += test_midi_channel_add();
+    return failures;
+}

tests/test_fifo.c

@@ -0,0 +1,160 @@
+#include "test_common.h"
+
+static int test_fifo_pipe(void) {
+    printf("Test: FIFO pipe add/remove\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_fifo", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    int fd = open("/tmp/looper_cmd", O_WRONLY);
+    if (fd < 0) {
+        perror("open fifo");
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    write(fd, "add\n", 4);
+    safe_usleep(1500000);
+    const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
+    int found = 0;
+    if (ports) {
+        for (int i = 0; ports[i]; i++) {
+            if (strstr(ports[i], "looper:channel1_input")) {
+                found = 1;
+                break;
+            }
+        }
+        jack_free(ports);
+    }
+    write(fd, "remove\n", 7);
+    close(fd);
+    safe_usleep(1500000);
+    ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
+    int still_found = 0;
+    if (ports) {
+        for (int i = 0; ports[i]; i++) {
+            if (strstr(ports[i], "looper:channel1_input")) {
+                still_found = 1;
+                break;
+            }
+        }
+        jack_free(ports);
+    }
+    jack_client_close(client);
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (!found) {
+        fprintf(stderr, "  FAIL: channel not added via FIFO\n");
+        return 1;
+    }
+    if (still_found) {
+        fprintf(stderr, "  FAIL: channel not removed via FIFO\n");
+        return 1;
+    }
+    printf("  PASS (FIFO add/remove works)\n");
+    return 0;
+}
+
+static int test_fifo_stop_bind_unbind(void) {
+    printf("Test: FIFO stop, bind, unbind\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_fifo_stop", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_fifo_stop:out");
+    snprintf(my_in,  sizeof(my_in),  "test_fifo_stop:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.1f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(150000);
+    int fd = open("/tmp/looper_cmd", O_WRONLY);
+    if (fd < 0) {
+        perror("open fifo");
+        jack_deactivate(client);
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    write(fd, "stop\n", 5);
+    write(fd, "bind 0\n", 7);
+    write(fd, "unbind\n", 7);
+    close(fd);
+    safe_usleep(500000);
+    int bursts_after = bursts;
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (bursts_after < 1) {
+        fprintf(stderr, "  FAIL: no burst detected (probably no recording)\n");
+        return 1;
+    }
+    printf("  PASS (FIFO stop, bind, unbind executed)\n");
+    return 0;
+}
+
+int test_fifo(void) {
+    int failures = 0;
+    failures += test_fifo_pipe();
+    failures += test_fifo_stop_bind_unbind();
+    return failures;
+}

tests/test_loop.c

@@ -0,0 +1,190 @@
+#include "test_common.h"
+
+static int test_looper_looping(void) {
+    printf("Test: loop recording and playback (expect ≥3 repetitions)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_looping", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: JACK not running?\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_looping:out");
+    snprintf(my_in,  sizeof(my_in),  "test_looping:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(500000);
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.1f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(150000);
+    safe_usleep(800000);
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(4000000);
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    int got_bursts = bursts;
+    printf("  detected bursts: %d\n", got_bursts);
+    if (got_bursts < 3) {
+        fprintf(stderr, "  FAIL: expected ≥3 bursts, got %d\n", got_bursts);
+        return 1;
+    }
+    printf("  PASS (at least 3 repetitions)\n");
+    return 0;
+}
+
+static int test_record_loop_stop(void) {
+    printf("Test: full record‑loop‑stop (≥5 repetitions)\n");
+    pid_t pid = start_looper();
+    if (pid < 0) return 1;
+    if (init_persistent_midi_client() != 0) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  FAIL: cannot initialise persistent MIDI client\n");
+        return 1;
+    }
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_full", JackNoStartServer, &status);
+    if (!client) {
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        fprintf(stderr, "  SKIP: no JACK\n");
+        return 1;
+    }
+    jack_port_t *audio_out = jack_port_register(client, "out",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *audio_in = jack_port_register(client, "in",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!audio_out || !audio_in) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    char my_out[64], my_in[64];
+    snprintf(my_out, sizeof(my_out), "test_full:out");
+    snprintf(my_in,  sizeof(my_in),  "test_full:in");
+    if (jack_connect(client, my_out, "looper:input") ||
+        jack_connect(client, "looper:output", my_in)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(500000);
+    int sr = jack_get_sample_rate(client);
+    continuous_sine = 0;
+    beep_remaining = (int)(0.5f * sr);
+    bursts = 0;
+    prev_above = 0;
+    passthrough_output_port = audio_out;
+    passthrough_input_port = audio_in;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = sr;
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client)) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 1, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(2500000);
+    if (send_jack_note_on("looper:control", 64, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    if (send_jack_note_on("looper:control", 65, 127) != 0) {
+        jack_client_close(client);
+        kill(pid, SIGTERM); waitpid(pid, NULL, 0);
+        return 1;
+    }
+    safe_usleep(200000);
+    int total_bursts = bursts;
+    jack_deactivate(client);
+    jack_client_close(client);
+    cleanup_persistent_midi_client();
+    kill(pid, SIGTERM);
+    waitpid(pid, NULL, 0);
+    if (total_bursts < 5) {
+        fprintf(stderr, "  FAIL: expected ≥5 bursts, got %d\n", total_bursts);
+        return 1;
+    }
+    printf("  PASS (≥5 repetitions, stopped cleanly)\n");
+    return 0;
+}
+
+int test_loop(void) {
+    int failures = 0;
+    failures += test_looper_looping();
+    failures += test_record_loop_stop();
+    return failures;
+}