ABLE-MCP

Right-click MIDI and audio tools for Ableton Live 12, plus an MCP server for .als analysis and live bridge orchestration.

Two artifacts in one repo:

1. AbleMCP.ablx — a native Ableton Live 12 extension. Drag it in, right-click clips, get fast deterministic transformations and vocal-to-complement generation. No API key, no cloud dependency.
2. able-mcp (Python) — an MCP server for parsing and analyzing .als project files offline. Plug into Claude Desktop / VS Code / Cursor and ask questions about your sets.

The extension (shipping in v0.2)

Built on @ableton-extensions/sdk 1.0.0-beta.0. Runs inside Live's own process — not Max for Live. Tested on Live 12.4.5b3.

Install

1. Download dist/AbleMCP.ablx
2. Open Live → Settings → Library → Extensions
3. Drag the .ablx file in
4. Restart Live

What you get

Right-click any MIDI clip (session or arrangement) → ABLE-MCP menu:

Action	What it does
ABLE-MCP: Variation	30% chance per note: bump ±octave; 15% chance: drop the note.
ABLE-MCP: Octave double	Add a quieter octave-up layer.
ABLE-MCP: Humanize	Jitter timing ±0.05 beats and velocity ±10.
ABLE-MCP: Reverse	Mirror notes around the clip's midpoint in time.
ABLE-MCP: Invert (mirror)	Mirror pitch around the median note.
ABLE-MCP: Transpose +1 / ABLE-MCP: Transpose -1	Semitone up / down.
ABLE-MCP: Legato	Extend each pitch's note to the next one's start.
ABLE-MCP: Staccato	Cut every note to 25% of its length.
ABLE-MCP: Thin (every other)	Drop every other note in time order.
ABLE-MCP: Double-time	Compress timing 2× and play the pattern twice.
ABLE-MCP: Half-time	Stretch to 2×; first half plays at half speed.
ABLE-MCP: Strum chords	Stagger simultaneous notes by 1/64 each (instant strum).
ABLE-MCP: Accent downbeats	Boost on-beat notes, duck off-beat.
ABLE-MCP: Top voice only	Keep the highest note of each chord.
ABLE-MCP: Bass voice (drop 8va)	Keep the lowest note of each chord, drop an octave.
ABLE-MCP: Shift…	Modal: shift notes by N beats and/or N semitones, with optional wrap-around. Quick-bump preset buttons for common values.

Every action also works on time-range selections in arrangement view — right-click a selection across one or more MIDI tracks and pick ABLE-MCP (range): …. Only notes inside the range are transformed.

Right-click any audio clip in arrangement view:

Action	What it does
ABLE-MCP: Chop into beats (1/4 bar) / 1/2 / 1 / 2 / 4 / 8 bars	Splits a long audio clip into adjacent cropped chunks without rewriting source audio.
ABLE-MCP: Snap first hit to bar	Detects first onset in WAV and repositions crop/start so the first hit lands on a downbeat.
ABLE-MCP: Create complementary MIDI from vocal...	Renders the clip range, extracts guide melody from audio, generates a complementary line, and writes a new arrangement MIDI clip (modal controls: similarity, density, register, call/response, seed, target track).

Every action is a single Cmd-Z undo.

Why it's fast

Core MIDI/audio actions are pure deterministic functions running in-process. Typical transform actions are near-instant and fully undoable. No LLM call is required for the shipping extension feature set.

Building from source

cd extension
npm install
npm run build      # tsc + esbuild → dist/extension.cjs
npm run package    # → ../dist/AbleMCP.ablx

The MCP server

Python 3.11, stdio transport. Parses Live's gzipped .als files and exposes structure as MCP tools. Useful when you want an LLM to read a project without opening Live.

Install

uv sync

Run

uv run able-mcp

Hook into a client

Claude Desktop — ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "able-mcp": {
      "command": "uv",
      "args": ["--directory", "/absolute/path/to/ABLE-MCP", "run", "able-mcp"]
    }
  }
}

VS Code (Copilot Chat) — your user or workspace mcp.json:

{
  "servers": {
    "able-mcp": {
      "command": "uv",
      "args": ["--directory", "/absolute/path/to/ABLE-MCP", "run", "able-mcp"]
    }
  }
}

Tools

Tool	What it does
als_summary(path)	Tempo, time sig, track/clip/note counts, master-bus state.
als_list_tracks(path)	Per-track kind, name, mute/solo, device & clip counts.
als_list_clips(path, track_index?)	Clip metadata across one or all tracks.
als_extract_midi(path, track_index, clip_index)	Note-level MIDI dump.
als_find_unfinished(path)	Heuristic suggestions for things that look incomplete.
midi_extract_vocal_guide(file_path, tempo_bpm, ...)	Extract monophonic guide melody from vocal WAV.
midi_generate_complement(guide_notes, ...)	Generate complementary (not duplicated) MIDI line.
midi_vocal_to_complement(file_path, tempo_bpm, ...)	One-shot extraction + complement generation pipeline.
live_arrangement_set_clip_notes(...)	Replace notes in arrangement MIDI clip by index.
live_vocal_to_complement_midi(...)	Render audio range in Live, generate complement, create/write arrangement MIDI clip in one call.

Roadmap

• v0.2.x — tighten vocal-to-complement quality (better vibrato handling, stronger anti-unison controls, warped-clip timing support).
• v0.3 — richer bridge orchestration tools (multi-clip workflows and arrangement/session interoperability).
• v0.4 — expand deterministic composition primitives (scale quantize, swing, density, stutter, chord-tone targeting).

Develop

uv run pytest         # Python tests
uv run ruff check .   # Python lint

Python tests use synthetic .als fixtures (gzipped XML) generated in tests/fixtures/init.py. When a real Live 12 file becomes available, drop it under tests/fixtures/real/ and add parity tests — the parser is best-effort against an undocumented schema.

Supply-chain hygiene

• uv.lock is committed; review every diff.
• All Python deps pinned with ==.
• The extension has exactly one runtime dep (@ableton-extensions/sdk), pinned in extension/package.json.

License

MIT (extension and Python server).