adjust_pitch
Adjust the pitch of any audio item by semitones (including fractional values) in a REAPER project to correct or creatively modify its tone.
Instructions
Adjust the pitch of an audio item by semitones (can be fractional).
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| track_index | Yes | ||
| item_index | Yes | ||
| semitones | Yes |
Implementation Reference
- src/reaper_mcp/audio_tools.py:136-152 (handler)The adjust_pitch function that executes the tool logic. It takes track_index, item_index, and semitones as parameters, retrieves the active take of the audio item, and sets its pitch to the specified semitone value.
@mcp.tool() def adjust_pitch(track_index: int, item_index: int, semitones: float) -> dict: """Adjust the pitch of an audio item by semitones (can be fractional).""" try: project = get_project() track = project.tracks[track_index] item = track.items[item_index] take = item.active_take take.pitch = semitones return { "success": True, "track_index": track_index, "item_index": item_index, "pitch_semitones": take.pitch, } except Exception as e: return {"success": False, "error": str(e)} - The function signature itself serves as the schema: parameters are track_index (int), item_index (int), and semitones (float), returning a dict with success status and pitch info.
@mcp.tool() def adjust_pitch(track_index: int, item_index: int, semitones: float) -> dict: """Adjust the pitch of an audio item by semitones (can be fractional).""" try: project = get_project() track = project.tracks[track_index] item = track.items[item_index] take = item.active_take take.pitch = semitones return { "success": True, "track_index": track_index, "item_index": item_index, "pitch_semitones": take.pitch, } except Exception as e: return {"success": False, "error": str(e)} - src/reaper_mcp/audio_tools.py:12-171 (registration)The register_tools function that registers adjust_pitch (and all other audio tools) via the @mcp.tool() decorator on the mcp instance.
def register_tools(mcp): @mcp.tool() def import_audio_file(file_path: str, track_index: int, position: float = 0.0) -> dict: """ Import an audio file onto a track at the given position (seconds). Supports all formats REAPER can read: wav, aiff, mp3, flac, ogg, etc. """ try: if not os.path.exists(file_path): return {"success": False, "error": f"File not found: {file_path}"} project = get_project() track = project.tracks[track_index] # Select only this track, set cursor, then insert media at cursor RPR.SetOnlyTrackSelected(track.id) project.cursor_position = position RPR.InsertMedia(file_path, 0) # Retrieve the item that was just created (last item on the track) track_refreshed = project.tracks[track_index] if track_refreshed.n_items == 0: return {"success": False, "error": "Insert succeeded but no item found on track"} item = track_refreshed.items[track_refreshed.n_items - 1] return { "success": True, "track_index": track_index, "item_index": track_refreshed.n_items - 1, "position": item.position, "length": item.length, "file_path": file_path, } except Exception as e: logger.error(f"import_audio_file failed: {e}") return {"success": False, "error": str(e)} @mcp.tool() def start_recording(track_index: int) -> dict: """Arm a track and start recording. Call stop_transport when done.""" try: project = get_project() track = project.tracks[track_index] track.armed = True RPR.Main_OnCommand(1013, 0) # Transport: Record return { "success": True, "track_index": track_index, "message": "Recording started. Call stop_transport to stop.", } except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def stop_transport() -> dict: """Stop playback or recording.""" try: RPR.Main_OnCommand(1016, 0) # Transport: Stop return {"success": True, "message": "Transport stopped"} except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def play_project() -> dict: """Start project playback from the current cursor position.""" try: RPR.Main_OnCommand(1007, 0) # Transport: Play return {"success": True, "message": "Playback started"} except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def set_cursor_position(position: float) -> dict: """Move the edit cursor to a position in seconds.""" try: project = get_project() project.cursor_position = position return {"success": True, "position": project.cursor_position} except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def edit_audio_item( track_index: int, item_index: int, start_trim: float = 0.0, end_trim: float = 0.0, fade_in: float = 0.0, fade_out: float = 0.0, ) -> dict: """ Trim an audio item and/or add fades. All values in seconds. start_trim: seconds to remove from the beginning. end_trim: seconds to remove from the end. fade_in/fade_out: fade length in seconds. """ try: project = get_project() track = project.tracks[track_index] item = track.items[item_index] if start_trim > 0: item.position += start_trim item.length -= start_trim take = item.active_take if take: take.start_offset += start_trim if end_trim > 0: item.length -= end_trim if fade_in > 0: item.fade_in_length = fade_in if fade_out > 0: item.fade_out_length = fade_out return { "success": True, "track_index": track_index, "item_index": item_index, "position": item.position, "length": item.length, } except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def adjust_pitch(track_index: int, item_index: int, semitones: float) -> dict: """Adjust the pitch of an audio item by semitones (can be fractional).""" try: project = get_project() track = project.tracks[track_index] item = track.items[item_index] take = item.active_take take.pitch = semitones return { "success": True, "track_index": track_index, "item_index": item_index, "pitch_semitones": take.pitch, } except Exception as e: return {"success": False, "error": str(e)} @mcp.tool() def adjust_playback_rate(track_index: int, item_index: int, rate: float) -> dict: """Adjust playback rate of an audio item. 1.0 = normal speed, 0.5 = half speed.""" try: project = get_project() track = project.tracks[track_index] item = track.items[item_index] take = item.active_take take.playback_rate = rate return { "success": True, "track_index": track_index, "item_index": item_index, "playback_rate": take.playback_rate, } except Exception as e: return {"success": False, "error": str(e)} - src/reaper_mcp/server.py:14-14 (registration)Import of register_tools from audio_tools module into the server.
from reaper_mcp.audio_tools import register_tools as _reg_audio - src/reaper_mcp/server.py:24-24 (registration)Call to _reg_audio(mcp) which registers all audio tools including adjust_pitch with the MCP server.
_reg_audio(mcp)