SuperCollider

SuperCollider MCP 🎛️

A Model Context Protocol server that lets AI assistants make sound with SuperCollider. Ask for "a dark ambient drone with slow swells" or "a breakbeat at 170 under a Cm7-Fm7 arpeggio" and it plays on your SuperCollider server.

• Real synths and drums. It ships its own SynthDefs (sine, saw, square, noise, FM, pad, Karplus-Strong pluck, kick, snare, hats, grains) plus an effect chain (distortion, low-pass, delay, reverb) and a safety limiter. Nothing depends on sclang's default synth or on sc3-plugins.
• Sample-accurate timing. Phrases are streamed to scsynth as timestamped OSC bundles, so every tool returns immediately. Calls can overlap, so you can layer drums, chords and melody.
• Music-aware tools. Melodies follow 14 scales, chords understand symbols like Am7, Bbmaj9 and G/B, drum patterns are readable step strings the assistant can write itself, and generative tools take a seed so a result you like can be replayed exactly.
• A panic button. stop_all silences everything this server started.

Requirements

• SuperCollider 3.10 or newer (tested with 3.13). Only the audio server, scsynth, has to be running.
• uv, or any Python 3.10+ with pip.

Quick start

1. Install and boot SuperCollider. Install it from the downloads page (or brew install --cask supercollider on macOS, sudo apt install supercollider on Debian/Ubuntu), then boot the server:

• in the SuperCollider IDE: *Server → Boot Server* (or run s.boot;)
• or without the IDE: scsynth -u 57110

2. Add the MCP server to your assistant.

Claude Code:

claude mcp add supercollider -- uvx supercollider-mcp

Claude Desktop, Cursor, Cline, Roo Code and other clients that use an mcpServers config:

{

"mcpServers": { "supercollider": { "command": "uvx", "args": ["supercollider-mcp"] } } }

To run the latest code from GitHub instead of the PyPI release, use "args": ["--from", "git+https://github.com/Tok/SuperColliderMCP", "supercollider-mcp"].

3. Ask for something. Start with "play a test sound" to check the connection, then try the prompts below.

Configuration

For example "args": ["supercollider-mcp", "--port", "57111"].

Tools

Most tools also take volume (0–1) and an optional effects object:

{"reverb": 0.6, "delay": 0.3, "delay_time": 0.25, "distortion": 0.0, "filter": 0.2}

All amounts are 0–1, and 0 means off. filter darkens the sound with a low-pass filter. delay_time is in seconds and defaults to three quarters of a beat.

Notes are names like C4 (middle C), F#3 or Bb2, or frequencies like "440" or "440hz".

Sequences separate notes with spaces or dashes. _ halves a note, + doubles it, :1.5 sets its length in beats, and . is a rest.

Drum patterns use one character per 16th note: X accent, x hit, o ghost note, . rest. Lanes (kick, snare, hat, open_hat, perc) can have different lengths and loop independently:

{"custom": {"kick": "X..x..X...x.....", "snare": "....X.......X..o", "hat": "x.x.x.x.x.x.x.x."}, "tempo": 92, "swing": 0.2}

Things to try

• "Play a dorian melody in D on the pluck synth with some delay, then the same one an octave lower."
• "Give me two bars of breakbeat at 170 BPM, then layer an Am7-Dm7-G7-Cmaj7 arpeggio on top."
• "A mysterious ambient soundscape, 60 seconds, low register."
• "Sweep a saw's filter with a slow triangle LFO while a granular cloud shimmers around A5."
• "Write me a half-time drum pattern with ghost notes on the snare."

How it works

assistant ──MCP (stdio)──▶ supercollider-mcp ──OSC/UDP──▶ scsynth ──▶ speakers

On first use the server checks that scsynth answers, uploads its SynthDefs (/d_recv) and creates its own node group with a voice group, an effects group and a limiter. Node IDs sit far above the ranges sclang uses, so your own SuperCollider work is not affected. If scsynth restarts, the setup runs again on the next call.

Each tool call turns into a *phrase*: a time-ordered stream of synth events (supercollidermcp/compose.py, pure Python). A background task sends each event about half a second ahead as an OSC bundle with an NTP timetag, and scsynth starts it at exactly that time. Every synth frees itself when its envelope ends. When a call asks for effects, its voices go to a private bus that one mcp_fx synth reads.

Upgrading from 0.1

• Point your MCP config at uvx supercollider-mcp as shown above. Old configs that run mcp run path/to/server.py still work through a small compatibility server.py.
• Sounds now come from real SynthDefs, so you no longer need sclang's default synth.
• Tools return right away instead of blocking until the sound ends.
• Some parameters changed meaning. create_drum_pattern takes bars (16 steps each) instead of beats. effects is an object instead of a JSON string. detune is now ±50 cents at 1.0 instead of up to an octave. The sc-osc command-line tool is gone.

See CHANGELOG.md for everything else.

Troubleshooting

• "No reply from the SuperCollider server…": scsynth is not running, or it listens on a different port. Boot it, or set SC_PORT.
• Calls succeed but you hear nothing: check that scsynth's outputs are connected to your sound card and that server_status shows synths while something plays.
• Linux with PipeWire (the default on current Ubuntu and Fedora): scsynth talks to JACK, so install PipeWire's JACK layer (sudo apt install pipewire-jack) and start SuperCollider through it: pw-jack scide, or pw-jack scsynth -u 57110 without the IDE. Otherwise scsynth tries to start its own jackd, which conflicts with PipeWire.
• `FAILURE IN SERVER /g_queryTree Group 2147480000 not found` in the post window on first connect is expected: it is how the server notices that scsynth still needs to be set up.
• Remote scsynth: timetags use wall-clock time, so keep both machines' clocks in sync (NTP).

Development

git clone https://github.com/Tok/SuperColliderMCP.git

cd SuperColliderMCP uv sync uv run pytest # unit and protocol tests run anywhere uv run ruff check . && uv run ruff format --check .

Some tests need SuperCollider:

• tests/test_synthdefs_nrt.py renders every SynthDef with scsynth -N (no audio device needed) and checks the audio. It runs automatically when scsynth is on PATH, or set SCSYNTH=/path/to/scsynth.
• tests/test_live_server.py runs every tool against a live server. Start a silent one with scsynth -u 57199 -i 0 -o 0, then run SC_TEST_PORT=57199 uv run pytest.

The SynthDefs are written in SuperCollider itself, in supercollidermcp/synthdefs/synthdefs.scd. After editing that file, rebuild the compiled .scsyndef files with python scripts/build_synthdefs.py (needs sclang; it runs headless).

supercollidermcp/

├── server.py MCP tools: validation and wiring ├── compose.py musical logic: requests → timed events (pure, unit-tested) ├── theory.py notes, scales, chords ├── patterns.py drum patterns as step strings ├── engine.py server setup, buses, streaming playback, stop_all ├── osc.py async OSC client that also reads scsynth's replies └── synthdefs/ synthdefs.scd (source) + compiled .scsyndef files

Contributions are welcome. New sounds usually mean a SynthDef in synthdefs.scd plus a composer function in compose.py.

License

MIT. See LICENSE.