# Multi‑Channel & Bind Feature

The looper supports up to 16 independent channels (numbered 0–15).  
Channel 0 is always present and connected to the `looper:input` / `looper:output` audio ports.  
Additional channels can be created and removed dynamically using MIDI commands.

## MIDI Ports

- **`looper:control`** – receives MIDI note‑on events for channel management and state toggling.
- **`looper:clock`** – receives MIDI clock messages (0xFA, 0xFC, 0xFB) that affect channel 0 only.

## Control‑Key Modifier

Hold the **control key** (MIDI note 64) pressed *before* sending another note to put the looper in “command mode”.  
While control‑key is active, the next note‑on (with velocity > 0) performs a special action instead of its direct mapping.  
The control key is released either by sending note‑off (note 64 or any note) or by sending a note‑on while control‑key is already active (the action is performed and control‑key is cleared).

## Available Commands (under control key)

| Note | Action                                                                                       |
|------|----------------------------------------------------------------------------------------------|
| 0–15 | **Bind** the next `control+62` toggle to the channel with that index.                       |
| 60   | **Add** a new dynamic channel (creates `channelX_input` / `channelX_output` ports).         |
| 61   | **Remove** the highest‑numbered active channel (excluding channel 0).                       |
| 62   | **Toggle** the current bound channel through its state machine:                              |
|      | IDLE → RECORD → LOOPING → PAUSED → LOOPING → … (each press advances one step).              |

> **Notes:**
> - The default bound channel is **0**. If you never send a bind command, `control+62` controls channel 0.
> - To bind a different channel, send `control + note <16>` (e.g., control + note 5 binds channel 5).
> - Bind is sticky – it stays until overwritten by another bind command.
> - There is **no unbind** command; you can rebind to channel 0 if needed.

## Direct Mapping (without control key)

For backward compatibility, the following notes work **without** the control‑key modifier:

| Note | Action                                                                                       |
|------|----------------------------------------------------------------------------------------------|
| 1    | Toggle channel 0 state (IDLE→RECORD→LOOPING→PAUSED→LOOPING…).                               |
| 60   | Add a dynamic channel (same as `control+60`).                                                |
| 61   | Remove the highest‑numbered active channel (same as `control+61`).                           |

## Example Usage

1. **Record a loop on channel 0 (using direct note 1)**  
   - Send note‑on, note 1, velocity 127 → channel 0 enters RECORD.  
   - Play some audio into `looper:input`.  
   - Send note‑on, note 1, velocity 127 again → channel 0 enters LOOPING.  
   - The recorded audio repeats indefinitely.

2. **Use the control‑key to toggle channel 0**  
   - Send `note‑on, note 64` (control key).  
   - Then send `note‑on, note 62` → toggles channel 0 (IDLE→RECORD).  
   - Send `note‑on, note 64` again, then `note‑on, note 62` again → RECORD→LOOPING.

3. **Add a new channel and bind it**  
   - Send `note‑on, note 64` + `note‑on, note 60` → creates channel 1.  
   - Send `note‑on, note 64` + `note‑on, note 1` → binds channel 1.  
   - Now `control+62` toggles channel 1 instead of channel 0.  
   - Record audio on channel 1 by sending `control+62` twice.

4. **Remove a dynamic channel**  
   - Send `note‑on, note 64` + `note‑on, note 61` → removes the highest‑numbered active channel (e.g., channel 1).

## Notes

- The looper must be connected to a running JACK server.  
- Channel buffers hold up to 5 seconds of audio at 48 kHz.  
- After removal, the channel’s audio ports are unregistered on the next main‑loop cycle (deferred to avoid race conditions).  
- The bind index is stored as an integer (0–15); values outside 0–15 are ignored (the note is processed as a command rather than a bind).