Vibe Composer MIDI MCP

Instructions

Implementation Reference

• src/mcp/tools/play-music.tool.ts:103-124 (handler)

  The handler function for the MCP 'play' tool. Initializes a new Midi instance, calls init(), plays the score using the provided input, and returns a text response.
  handler: async ( input: PlayMusicMcpToolInput ): Promise<{ content: { type: "text"; text: string }[] }> => { const midi = new Midi(); await midi.init(); await midi.playScore({ bpm: input.bpm, midiOuputName: input.midiOuputName, tracks: input.tracks as any, }); return { content: [ { type: "text", text: "Playing music score", }, ], }; },
• src/mcp/tools/play-music.tool.ts:5-92 (schema)

  Zod input schema defining the structure for bpm, midiOutputName, and tracks including instruments, channels, notes, drums, and durations.
  const inputSchema = { bpm: z.number().describe("The BPM of the song"), midiOuputName: z .string() .optional() .describe("The MIDI output name to use. Don't add unless requested."), tracks: z .array( z.object({ instrumentName: z .enum([ "drums", ...(Object.keys(Instruments) as [string, ...string[]]), ]) .describe( `The instrument of the track. Available instruments: ${Object.keys( Instruments ).join( ", " )}. If you want to make it a drum track, set the instrumentName to 'drums'.` ), channel: z .number() .optional() .describe( "The MIDI channel of the track. Don't add unless requested." ), notes: z .array( z.object({ note: z .array(z.string()) .nullable() .optional() .describe( "The notes to play. Use array for chords. Or put one element for single note. Use an empty array for rest/silence" ), drums: z .array(z.string()) .nullable() .optional() .describe( "The drums to play. Use array for multiple drums. Use an empty array for rest/silence. Available drums: " + Object.keys(Drums).join(", ") ), noteDuration: z .string() .describe( "The note duration, e.g.: 1/32, 1/16, 1/8, 1/4, 1/2, 1" ), }) ) .describe( `"Array of notes or drums to play with timing. - If you want to play a drum track, use the drums property. - If you want to play a non-drum instrument, use the note property. Example: [{note: ['C2', 'E2'], noteDuration: '1/8'}, {note: [], noteDuration: '1/8'}, {note: ['G2'], noteDuration: '1/8'}, {note: null, noteDuration: '1/8'}]. Or [{drums: ['bass_drum_1', 'closed_hi_hat'], noteDuration: '1/8'}, {drums: ['closed_hi_hat'], noteDuration: '1/8'}, {drums: ['closed_hi_hat', 'acoustic_snare'], noteDuration: '1/8'}, {drums: ['closed_hi_hat'], noteDuration: '1/8'}]. An array could be a bar or several bars. -------------------------------------------------------------------------------- IMPORTANT FOR FOR DRUM TRACKS: - notes are played one after another. - we wait until the whole duration of a note before we play another one. - So don't do this: "notes" :[{"drums: ["bass_drum_1", "closed_hi_hat"], noteDuration: '1/4'},{"drums: [ "closed_hi_hat"], noteDuration: '1/4'} {drums: ['closed_hi_hat', 'acoustic_snare'], noteDuration: '1/4'}...].` ), }) ) .describe( `Array of tracks to play. - If you want to make it a drum track, set the instrumentName to 'drums'. and Use the 'drums' proprerty in notation. - Otherwise, use the 'note' property in 'notes'. - Unless asked otherwise, add 10 bars assuming 4/4 time signature. - Unless asked otherwise, make sure that each has the same number of bars. - Sometimes you make some tracks longer or shorter than others. Avoid that. ` ), };
• src/mcp-server.cli.ts:22-30 (registration)

  Registers the 'play' tool (via PlayMusicMcpTool) with the MCP server, providing name, metadata including inputSchema, and handler.
  server.registerTool( PlayMusicMcpTool.name, { title: PlayMusicMcpTool.title, description: PlayMusicMcpTool.description, inputSchema: PlayMusicMcpTool.inputSchema, }, PlayMusicMcpTool.handler );
• src/midi/midi.ts:199-205 (helper)

  The playScore method in the Midi class, which is called by the tool handler. It opens the MIDI output, sets BPM, and concurrently plays all tracks.
  public async playScore(score: Score) { await this.openMidiOut(score.midiOuputName); this.setBpm(score.bpm); return Promise.all(score.tracks.map((track) => this.playTrack(track))); }