ableton-mcp-server

An MCP server that exposes Ableton Live to AI agents, built as a native Ableton Extension on top of the official @ableton-extensions/sdk (released in beta, June 2025).

It lets an agent (Claude, etc.) read and edit a Live set — tracks, clips, MIDI notes, devices/parameters, scenes — and render/import audio, all over a local MCP endpoint.

Status: beta. Targets Extensions SDK API 1.0.0.

How it works

An Ableton Extension is an activate(context) function that runs inside Live's Extension Host — a full Node.js ≥22 process embedded in Live. This project's activate() initializes the SDK and starts an in-process MCP server over Streamable HTTP, bound to 127.0.0.1. The tool handlers call straight into Live's data model — no second process, no IPC.

┌─────────────── Ableton Live ───────────────┐
│  Extension Host (Node 22)                   │
│   activate() ─ initialize(sdk) ─ Live data  │
│        │                                    │
│   MCP server  ── Streamable HTTP ──┐        │
└────────────────────────────────────┼───────┘
                                      │ 127.0.0.1:39001/mcp
                          ┌───────────▼──────────┐
                          │  MCP client (Claude) │
                          └──────────────────────┘

Two consequences shape the design:

• stdio is owned by the host, so the MCP transport is HTTP, not stdio.

• The lifecycle is inverted — Live owns the process — so the MCP client connects to an already-running endpoint rather than spawning it. The server is only alive while Live + the extension are running; clients must tolerate it appearing/disappearing.

Object addressing

Tools reference Live objects by stable path strings:

Tools (31)

What an agent can do

Read the set's state; compose (create tracks/clips, write MIDI notes), edit (rename, mute/solo/arm, clip name/color/loop on-off), sound-design (insert devices, set parameter values), and render/import audio (e.g. render a range of an audio track to WAV).

Known limits (from the SDK, not this server)

• No transport/playback: no play/stop/fire/record — the agent composes and edits, it doesn't perform.

• Loop points are read-only after creation (set_clip_properties only toggles looping).

• No push events: request/response only; poll to observe changes.

• render_pre_fx_audio renders pre-effects audio of an arrangement range.

Setup

Requires Node ≥22.11 and a version of Ableton Live that supports extensions.

npm install
npm test          # unit + real HTTP-loopback tests (no Live needed)
npm run build     # bundles src/extension.ts -> dist/extension.js (CJS)

Run inside Live (development)

You need the Live Beta build that supports extensions (from Ableton's Centercode release page). Ableton recommends Node ≥ 24.14.1 for the toolchain; this project also builds/tests fine on Node 22 (Live runs the extension on its own bundled Node).

1. Enable Developer Mode in Live: Preferences → Extensions → Developer Mode. Required — otherwise the CLI can't connect to Live.

2. Point the CLI at Live, either by copying .env.example to .env and setting EXTENSION_HOST_PATH, or by passing --live:

   npm start                                   # uses .env
   # or
   npm start -- --live "/Applications/Ableton Live 12 Suite Beta.app"

npm start builds the extension and launches Live's Extension Host with it. On start you'll see, in the terminal/host log:

[ableton-mcp] MCP server listening on http://127.0.0.1:39001/mcp

Config via env: ABLETON_MCP_HOST (default 127.0.0.1), ABLETON_MCP_PORT (default 39001). Pass --inspect for VS Code debugging.

Connect an MCP client

Because the server is already running, register it as an HTTP MCP server (do not let the client spawn it). For Claude Code:

claude mcp add --transport http ableton-live http://127.0.0.1:39001/mcp

Or inspect it with the MCP Inspector:

npx @modelcontextprotocol/inspector
# transport: Streamable HTTP, URL: http://127.0.0.1:39001/mcp

Then try: get_song_state, set_tempo {bpm:124}, create_midi_track, create_midi_clip {track:"track/0", slot:0, length:4}, set_notes {clip:"track/0/clipslot/0/clip", notes:[{pitch:60,startTime:0,duration:1}]}.

Package for distribution

npm run package   # production bundle -> Ableton-MCP-0.1.0.ablx (manifest + entry)

A .ablx is the shareable/installable archive. During the SDK beta the primary way to load an extension is Developer Mode + npm start above.

Development

Built test-first with vitest. The architecture keeps the host out of the test path:

• Pure logic (addressing.ts, notes.ts) — tested with no mocks.

• Tools depend only on the narrow Live interface and are tested against an in-memory FakeLive.

• MCP server is tested with a real Client+McpServer over InMemoryTransport, and the HTTP layer with a real loopback (real MCP client over StreamableHTTPClientTransport).

• The only host-bound code (live.context.ts, extension.ts) is covered by the real-Live integration test, not unit tests — the native host can't run in CI.

src/
  addressing.ts      object path parse/serialize (pure)
  notes.ts           MIDI note validation (pure)
  live.ts            the Live facade interface + DTOs
  live.fake.ts       in-memory Live for tests
  live.context.ts    real Live over the Extension Host
  tools/             one file per tool group + registry
  server.ts          builds the McpServer from the tool registry
  http.ts            Streamable HTTP transport on localhost
  extension.ts       activate() entry point

License

The Ableton Extensions SDK and CLI are © Ableton AG (see their LICENSE.md). This project is provided as-is.