# Fcp Midi

> MCP server for semantic MIDI music composition

- **Type:** MCP server
- **Install:** `agentstack add mcp-os-tack-fcp-midi`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [os-tack](https://agentstack.voostack.com/s/os-tack)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [os-tack](https://github.com/os-tack)
- **Source:** https://github.com/os-tack/fcp-midi

## Install

```sh
agentstack add mcp-os-tack-fcp-midi
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# fcp-midi

MCP server for semantic MIDI composition.

## What It Does

fcp-midi lets LLMs compose music by describing musical intent -- notes, chords, dynamics, tempo changes -- and renders it into standard MIDI files. Instead of manipulating raw bytes or MIDI events, the LLM works with operations like `note Bass E2 at:1.1 dur:quarter vel:90` and `crescendo @track:Lead vel:45-75 @range:3.1-6.4`. Built on the [FCP](https://github.com/os-tack/fcp) framework; a `mido.MidiFile` is the source of truth throughout, so there's no separate serialization step.

## Quick Example

```
midi_session('new "Voltage Drop" tempo:140 key:E-minor')

midi([
  'note Drums kick at:1.1 dur:eighth vel:100',
  'note Bass E2 at:1.1 dur:quarter vel:90',
  'chord Pad Em at:1.1 dur:whole vel:70',
  'crescendo @track:Lead vel:45-75 @range:3.1-6.4',
  'tempo 174 at:11.1',
])

midi_session('save as:./voltage_drop.mid')
```

### Available MCP Tools

| Tool | Purpose |
|------|---------|
| `midi(ops)` | Batch mutations -- notes, chords, tracks, tempo, dynamics, copy/transpose |
| `midi_query(q)` | Inspect the composition -- map, tracks, events, piano-roll, instruments, find |
| `midi_session(action)` | Lifecycle -- new, open, save, checkpoint, undo, redo |
| `midi_help()` | Full reference card |

### Hero Examples

**Plumber's Journey** -- Classic game theme faithfully recreated: 4 tracks, 288 notes, 16 seconds, 180 BPM.

**Voltage Drop** -- A drum-and-bass track with tempo acceleration (140 -> 155 -> 174 BPM), 5 tracks, breakbeats, sub-bass, arpeggios, and a signature DROP section. Also used in the FCP vs raw Python agent battle -- FCP produced 1,674 notes across 12 tracks in 87 seconds, compared to 694 notes from ~689 lines of hand-written Python.

See [`docs/examples/`](docs/examples/) for MIDI files and the full writeup.

## Installation

Requires Python >= 3.11.

```bash
pip install fcp-midi
```

### MCP Client Configuration

```json
{
  "mcpServers": {
    "midi": {
      "command": "uv",
      "args": ["run", "python", "-m", "fcp_midi"]
    }
  }
}
```

## Architecture

Mido-native — no parallel semantic model between the op handlers and the file format:

```
MCP Server (fcp-core create_fcp_server + MidiAdapter)
  Parses op strings, dispatches to verb handlers, session lifecycle
        |
MidiModel (mido.MidiFile is the source of truth)
  Op handlers read/write mido messages directly on the tracks;
  a NoteIndex gives fast selector lookups. Undo/redo and batch
  atomicity are byte snapshots of the file, not event replay.
```

Key features:

- **Instrument library** -- GM instruments by name (`acoustic-grand-piano`, `synth-bass-1`, `standard-kit`)
- **Soundfont support** -- Load custom instrument banks
- **Beat addressing** -- `at:1.1` (bar 1, beat 1), `at:3.2.240` (bar 3, beat 2, tick 240)
- **Duration vocabulary** -- `whole`, `half`, `quarter`, `eighth`, `sixteenth`, `triplet`
- **Dynamics** -- `crescendo`, `diminuendo` across ranges
- **Copy/transpose** -- Duplicate and shift musical phrases

## Development

```bash
uv sync
uv run pytest       # 620 tests
uv run pytest -m "not slow"  # skip stress tests (604 tests, ~0.25s)
uv run ruff check   # linting
uv run pyright      # type checking
```

## License

MIT

## Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [os-tack](https://github.com/os-tack)
- **Source:** [os-tack/fcp-midi](https://github.com/os-tack/fcp-midi)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/mcp-os-tack-fcp-midi
- Seller: https://agentstack.voostack.com/s/os-tack
- Browse the marketplace: https://agentstack.voostack.com/browse

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