sp-mc

This connects any MCP client with Sonic Pi enabling you to create music with English.

Tell Claude : "Use mcp to create an Acid House track with 120 bpm in the key of F"

Sonic Pi MCP Server

I wanted to use mcp-sonic-pi but had version issues on my system so ported it to Node

So far only tested on a Linux system with Claude Code.

Current status

• Live OSC tools (initialize_sonic_pi, play_music, etc.) unchanged and working as before.
• New render_midi tool can read Sonic Pi .rb files and export .mid with per-instrument tracks (drums split per instrument). It now honors with_bpm blocks, simple .times repetition, common live_loop patterns, and maps popular drum samples to separate tracks.

Known limitations (planned improvements):

• Complex Ruby control flow/randomness is skipped with warnings.
• Timing is best-effort for straightforward sleep/.times; no randomness/conditionals.
• Limited chord vocabulary and drum sample map; falls back to grand piano or default drum pitch when unknown. notes.choose draws from the last scale assignment (random choice); one_in(n) blocks execute probabilistically.

Features

• Direct OSC communication with Sonic Pi (no psonic dependency)
• Supports both Sonic Pi v3.x and v4.x
• Automatic port detection from Sonic Pi log files

The server provides six tools:

• initialize_sonic_pi - Initialize connection to Sonic Pi
• play_music - Execute Sonic Pi code
• stop_music - Stop all playback
• get_beat_pattern - Get beat patterns (blues, rock, hiphop, electronic)
• make_acid - Generate an Acid House style track
• render_midi - Read a Sonic Pi .rb file and render a .mid file with one track per instrument (drums split per instrument)

Sonic Pi → MIDI rendering

Use the render_midi MCP tool to export a .mid file from an existing Sonic Pi Ruby script:

{
  "name": "render_midi",
  "arguments": {
    "path": "/path/to/song.rb",
    "bars": 8,
    "output": "/tmp/song.mid"
  }
}

Drums are split into separate tracks (kick, snare, hats, etc.). Use loop_names to render specific live_loops or drum_split: false to merge all percussion into one track.

Known limitations (planned improvements):

• Complex Ruby control flow/randomness is skipped with warnings.
• Timing is best-effort for straightforward sleep/.times; no randomness/conditionals.
• Limited chord vocabulary and drum sample map; falls back to grand piano or default drum pitch when unknown.

Prerequisites

• Sonic Pi
• Node

Setup

The easy way is :

claude mcp add sp-mc npx 'sp-mc@latest'

or

codex mcp add sp-mc npx 'sp-mc@latest'

Start Sonic Pi then start Claude/Codex.

Installation

git clone https://github.com/danja/sp-mc.git
cd sp-mc
npm install

Configure MCP Connection

eg. in ~/.claude.json:

   "sonic-pi": {
     "type": "stdio",
     "command": "node",
     "args": ["/path/to/sp-mc/mcp/server.js"],
     "env": {}
   }

Running in VS Code

There is a VS Code extension vscode-sonic-pi which provides syntax highlighting for Sonic Pi code. With Claude Code running in a VS Code terminal you can build up songs in the editor and manage them on the file system.

Port Configuration Note

The MCP server automatically detects the correct port from Sonic Pi's log files. If Sonic Pi is running on a non-standard OSC port (e.g., 4560 instead of the default 4557), the server will find and use the correct port automatically by parsing ~/.sonic-pi/log/server-output.log.

Testing

This project includes comprehensive test coverage with vitest. Tests can run against either a mock Sonic Pi server or a real Sonic Pi installation.

Run tests (mock mode by default):

npm test

Run tests in watch mode:

npm run test:watch

Run tests with mock Sonic Pi server:

npm run test:mock

Run tests with real Sonic Pi (requires Sonic Pi to be running):

npm run test:real

Test Structure:

• mcp/log-parser.test.js - Tests for Sonic Pi log file parsing
• mcp/sonic-pi-client.test.js - Tests for OSC communication with Sonic Pi
• mcp/server.test.js - Tests for MCP server beat patterns and validation
• mcp/render/render.test.js - Tests for Sonic Pi → MIDI rendering
• mcp/render/render-roundtrip.test.js - Round-trip timing checks (e.g., with_bpm alignment)
• mcp/render/utils.test.js - Note/chord/sample mapping tests
• test/helpers/ - Mock Sonic Pi server and test utilities
• test/fixtures/ - Sample log files for testing

Note: If you have Sonic Pi installed, some tests may use your real Sonic Pi logs for integration testing. To run pure unit tests, temporarily move ~/.sonic-pi/log/ or use Docker/CI environments.

Documentation

See /mcp/README.md for detailed documentation.