Start Lemon Studio listening on the control socket (does nothing if it already is).

project: an .flp file to open. headless: run with no window (--serve) instead of the app with its window.

Whether Lemon Studio is connected, the app's version, this client's permission level, and the transport.

The whole project: tempo, ppq, time signature, channels, mixer tracks (with effect slots and sends), patterns, the playlist's clips, the current pattern and song/pattern mode. Positions here are raw ticks.

The notes of pattern pattern (an id): channel id, position, length, key, velocity, pan.

The instrument and effect plugin names that add_channel and add_effect take.

The parameters (id, name, value 0..1, value text, ...) of the plugin playing channel id or effect slot id owner.

The undo history: each step's name and whether it is undone.

What changed after event number since (0: all kept), including the user's own edits in the app, and last, the newest event number to pass next time.

Write notes into pattern pattern (an id).

notes: [{"channel": id, "position": 0, "length": 0.5, "key": 60, "velocity": 100, "pan": 64}, ...]; position/length in unit (beats by default). channel fills in notes that leave theirs out. replace=True: these become the notes of channel in the pattern (or all of its notes when channel is None); replace=False: they are added to what is there.

Remove the notes of channel from pattern pattern (or all of its notes when channel is None).

Add a channel played by instrument plugin (a name from list_plugins, e.g. "Lemon Trio"), or a sampler with sample (an audio file path) loaded. mixer_track: a mixer track id to route it to. Returns its id.

Change channel channel (an id): volume 0..1, pan -1..1, pitch in cents, color "#rrggbb", enabled (False mutes it), mixer_track (a mixer track id). Only the fields given change.

Delete channel channel (an id), with its notes, clips and automation.

Load audio file path into sampler channel channel (an empty path clears it).

Add a pattern. Returns its id.

Rename, recolor, or set the length of pattern pattern (an id). length 0 = automatic.

Delete pattern pattern (an id) and its playlist clips.

Place pattern pattern (an id) in the playlist on track track (1-based) at position. Returns the clip id.

Move, resize or mute playlist clip clip (an id).

Remove playlist clip clip (an id).

Add a mixer insert (at insert number at, else after the last). Returns its id.

Change mixer track track (an id): volume 0..1 (0.8 = unity), pan and stereo -1..1, enabled (False mutes).

Send mixer track from_track to to_track (ids) at level 0..1; level None removes the route.

Set band 0..2 of mixer track track's built-in 3-band EQ: gain in dB (-18..18), frequency and width as stored (0..65536).

Add effect plugin (a name from list_plugins) to mixer track track (an id), in slot 0..9 or the first free one. Returns the slot plugin's id (for get_plugin_params / set_plugin_param).

Turn effect slot slot (0..9) of mixer track track (an id) on or off, or set its mix 0..1.

Remove the effect in slot slot (0..9) of mixer track track (an id).

Set parameter param (an id from get_plugin_params) of the plugin of channel or slot owner to value 0..1.

Set the tempo (10..522 BPM).

Set the time signature (denominator 2, 4, 8 or 16).

Swing 0..1, main volume 0..1 (0.8 = unity), main pitch in cents, and the song info.

Start playback, as the Play button (resumes when paused).

mode: "pattern" loops the current pattern, "song" plays the playlist (default: the app's PAT/SONG switch). pattern: make this pattern (an id) the current one. from_position: where to start.

Pause playback in place (play resumes).

Stop playback and rewind to where it started.

Change what the user sees, not the music: make pattern (an id) the current pattern, select channel (an id) in the channel rack, and with piano_roll=True open the piano roll on them (False closes it). While the piano roll is shown it scrolls to the channel's notes. No undo step. Use it after writing notes so the user sees them.

Playing, paused or stopped; pattern or song mode; the current pattern; the playhead position; the tempo.

Undo the last step (anyone's: this client's or the user's).

Redo the last undone step.

Save the project (to path, else its own file). With the app's window open, the user is asked first.

Run raw control-plane commands (Lemon Studio docs/control-plane.md) as ONE undo step, all or nothing. Positions and lengths here are raw ticks. Each command is {"op": ..., fields...}, e.g. {"op": "add_channel", "name": "Bass", "plugin": "Lemon Trio"}. Returns each command's result.

Like apply_commands, but Lemon Studio asks the user to Apply or Discard. Returns the proposal number and what it would change.

Render a saved .flp project to an audio file (.wav), with no window and no audio device. Save the open project first (save_project) to render what is in the app.