Check that the bridge is reachable. Returns bridge_version and reaper_version.

Return metadata about the currently open REAPER project.

Return loop range, cursor position, and loop-enabled state.

List every track in the project with volume, pan, mute, solo, arm state.

Get detailed info for a single track by 0-based index.

Insert a new track.

• name: track name (default "Track N")

• index: 0-based position (default: append at end)

Delete a track by 0-based index. This is permanent and undoable via REAPER's undo system.

Modify one or more properties of a track.

• volume: linear amplitude (1.0 = 0 dB)

• pan: -1.0 (full left) to 1.0 (full right)

Move a media item to a new timeline position (seconds).

Change the length of a media item (seconds).

Delete a media item from a track.

Return properties of a media item: position, length, mute, lock, take name, playrate, and pitch.

Duplicate a track, inserting the copy immediately after the original.

Duplicate a media item on its track.

Insert a MIDI CC, pitch-bend, or program-change event into a MIDI item.

• event_type: 'cc' | 'pitch_bend' | 'program_change'

• ppq: position in PPQ ticks

• channel: 0-15

• cc: provide cc_number (0-127) and value (0-127)

• pitch_bend: provide bend (-8192 to 8191, 0 = center)

• program_change: provide program (0-127)

Delete a specific MIDI note from a MIDI item by its 0-based note index.

Modify an existing MIDI note. Only the supplied fields are changed.

• pitch: MIDI note number (0-127)

• velocity: 0-127

• channel: 0-15

• start_ppq / end_ppq: positions in PPQ ticks

Read all MIDI notes from a media item's active MIDI take. Returns a list of notes with start_ppq, end_ppq, pitch, velocity, channel.

List all media items on a track with their position, length, and take info.

Batch-edit multiple MIDI notes in one call. More efficient than calling set_midi_note() repeatedly. Each entry in 'notes' must have 'note_index' and any subset of: pitch, velocity, start_ppq, end_ppq, channel, selected, muted. Omitted fields keep their current values.

Humanize all MIDI notes in an item with random timing and/or velocity offsets.

• timing_range_ppq: maximum ±PPQ timing shift per note (0 = no timing change). At 960 PPQ, 20 PPQ ≈ 1/48th note of swing.

• velocity_range: maximum ±velocity shift per note (0 = no velocity change). Velocity is clamped to 1-127.

• seed: optional integer for reproducible results (omit for random each call). Returns the per-note changes applied.

Create a MIDI item on a track and optionally pre-populate it with notes.

• start / end: time in seconds

• notes: list of {start_ppq, end_ppq, pitch, velocity=100, channel=0}

Insert an audio file onto a track at the given position (seconds).

Control REAPER's transport. action: play | stop | pause | record | goto_start | goto_position position: required when action == goto_position (seconds)

Add an FX plugin to a track.

• track_index: 0-based track index, or -1 for the master track

• fx_name: any string REAPER's FX browser accepts ("ReaComp", "VST: Serum", etc.)

• input_fx: True to add to the input FX chain

List all FX plugins on a track (name, fx_index, n_params, enabled). Use track_index=-1 for the master track.

Return all parameters for an FX plugin on a track. Each entry includes: param_index, name, value, min_value, max_value, normalized.

Set an FX parameter by normalized value (0.0–1.0).

Enable or bypass (disable) a specific FX plugin on a track.

Remove an FX plugin from a track's FX chain.

Load a named preset for an FX plugin on a track. preset_name can be:

• A plain preset name or index-based name (for plugins with internal preset banks)

• A full absolute file path to a .ffp/.fxp/.fxb file (FabFilter and others). Use the 'path' field from list_fx_presets() for file-based plugins. On failure, returns loaded=false with a failure_reason: 'preset_name_not_found' - name not in the plugin's preset list 'plugin_rejected_state' - plugin returned false despite the name existing 'plugin_has_no_presets' - plugin exposes no preset bank at all 'file_unreadable' - path given but file could not be opened

List available presets for an FX already on a track. Returns two lists:

• factory_presets: presets exposed by the plugin itself (CLAP, VST3, VST2 banks). Each entry has {index, name, source='factory'}. These can be loaded by name with set_fx_preset().

• file_presets: .ffp/.fxp files found on disk under standard vendor preset dirs. Each entry has {name, category, path, source='file'}. Load via the 'path' field.

Return the current BPM and time signature.

Set the project tempo (and optionally time signature).

• bpm: beats per minute

• time_sig_num / time_sig_denom: e.g. 3, 4 for 3/4 time

Set a named project parameter. Supported parameters: loop_start, loop_end, loop_enabled, cursor_position, playrate

Save the current REAPER project to disk.

Render a time range to an audio file using REAPER's render pipeline.

• output_path: absolute path including extension (e.g. '/tmp/mix.wav'). REAPER uses the current render format; set a .wav extension for PCM output.

• start_time / end_time: seconds

• sample_rate: 0 = use project rate

• channels: 1=mono, 2=stereo Returns output_path and file_size_bytes so you can verify the file was written. After rendering, attach the file to this conversation so the audio can be heard.

Measure the loudness of a single track over a time range using a non-destructive dry-run render (action 42439). No items, tracks, or files are created — project state is completely unchanged after the call. Returns:

• lufs_i: integrated loudness in LUFS

• lufs_s_max: maximum short-term loudness in LUFS

• lufs_m_max: maximum momentary loudness in LUFS

• true_peak_db: true peak in dBTP

• raw_stats: raw key=value string from REAPER for any additional fields

Measure the loudness of the full master mix over a time range using a non-destructive dry-run render (action 42441). No tracks or files are created. Returns:

• lufs_i: integrated loudness in LUFS

• lufs_s_max: maximum short-term loudness in LUFS

• lufs_m_max: maximum momentary loudness in LUFS

• true_peak_db: true peak in dBTP

• raw_stats: raw key=value string from REAPER for any additional fields

Normalize a track to a target integrated loudness by measuring its current LUFS via a non-destructive dry-run render, then adjusting the track fader.

• target_lufs: desired integrated loudness in LUFS (default -14.0, streaming standard). Use -23.0 for EBU R128 broadcast, -16.0 for podcast. Returns measured_lufs_i, gain_applied_db, and old/new fader volumes. The change is registered in REAPER's undo history.

Trigger REAPER's undo. Returns the name of the action that was undone.

Add a marker or region to the project.

• position: time in seconds

• is_region: True to create a region; also requires region_end

• region_end: end time in seconds (only for regions)

• color: REAPER color integer (0 = default)

List all markers and regions in the project.

Delete a marker or region by its 0-based enumeration index (from list_markers).

Open a REAPER project file (.rpp) by its absolute path.

Create a new blank REAPER project (equivalent to File > New Project).

List installed FX plugins (VST, VST3, CLAP, and JS/JSFX).

• filter: optional case-insensitive substring to match against plugin name or type e.g. 'fabfilter', 'vst3', 'clap', 'rea', 'comp'

Returns a list of {name, type} objects and a total count. type values: 'VST' (VST2), 'VST3', 'CLAP', 'JS'

Create a send from one track to another. Returns the new send index.

Copy all items overlapping [start_time, end_time) and paste them immediately after end_time, repeating repeat_count times. Useful for extending song form (repeating a chorus, creating an outro).

• start_time / end_time: seconds

• repeat_count: how many copies to paste (default 1) Returns the new project end time after pasting.

Remove a send from a track by its 0-based send index.

Set the volume and/or pan of a track send.

• volume: linear amplitude (1.0 = 0 dB)

• pan: -1.0 (full left) to 1.0 (full right)

Set the recording input for a track.

• For audio: 0-based audio input channel index.

• For MIDI: use REAPER's I_RECINPUT encoding (e.g. 4096 + channel*32 + device).

Set input monitoring mode for a track.

• mode: 0 = off, 1 = on, 2 = not when playing

Read all automation envelope points from a track envelope. Identify the envelope by name (e.g. 'Volume', 'Pan', 'Mute') or by 0-based envelope_index. Using envelope_name is preferred and works even if the envelope is not yet visible/armed in the REAPER UI. Returns envelope name and list of points with time, value, shape, tension.

Insert a point into an automation envelope. Identify the envelope by name (e.g. 'Volume', 'Pan', 'Mute') or by 0-based envelope_index. Using envelope_name is preferred and works even if the envelope is not yet visible/armed in the REAPER UI.

• time: position in seconds

• value: linear amplitude (Volume: 0.0=silence, 1.0=0 dB, 2.0=+6 dB max)

• shape: 0=linear, 1=square, 2=slow start/end, 3=fast start, 4=fast end, 5=bezier

• tension: bezier tension (-1.0 to 1.0)

Insert an automation envelope point aligned to the project beat grid. Identify the envelope by name (e.g. 'Volume', 'Pan') or by 0-based envelope_index.

• bar: 1-based measure number (bar 1 = project start)

• beat: 1-based beat within the bar, may be fractional (e.g. 2.5 = beat 2 and a half). Beat units follow the time-signature denominator (e.g. quarter notes in 4/4, eighth notes in 6/8).

• value: linear amplitude (Volume: 0.0=silence, 1.0=0 dB, 2.0=+6 dB max)

• shape: 0=linear, 1=square, 2=slow start/end, 3=fast start, 4=fast end, 5=bezier Returns the resolved time in seconds alongside bar/beat for verification.

Delete all automation envelope points in the given time range (default: entire timeline). Identify the envelope by name (e.g. 'Volume', 'Pan') or by 0-based envelope_index.