chord-synth

Generate chord progression WAV files. Zero dependencies. Node.js only.

28 named presets, 22 arpeggio patterns, 7 instruments, slash chords (Am/E), transposition, pad/bass/drum tracks, reverb.

Quick Start

# Install globally
npm install -g chord-synth

# Generate a WAV file
chord-synth --preset "C G Am F" --bpm 120 --output pop.wav

# Custom jazz with slash chords
chord-synth --preset "Dm9 | G7/B | Cmaj7 | Am7/E" --instrument piano --drums bossanova --output jazz.wav

# Named preset transposed to key of G
chord-synth --preset "I-V-vi-IV (Pop)" --transpose 7 --output pop_in_G.wav

# Batch render from JSON file
chord-synth --batch render_jobs.json --output ./wavs/

Use as MCP Server

Exposes generate_wav and list_options tools to any MCP-compatible agent (Claude Desktop, Claude Code, Cursor, Windsurf, etc).

Claude Desktop — add to claude_desktop_config.json:

{
  "mcpServers": {
    "chord-synth": {
      "command": "node",
      "args": ["/path/to/chord-synth/mcp-server.js"]
    }
  }
}

Claude Code:

claude mcp add chord-synth -- node /path/to/chord-synth/mcp-server.js

Then ask Claude: "Generate a sad violin arpeggio over Am F C G at 80 BPM" — it will call generate_wav directly.

Use as Node.js Module

const { renderJob, PRESETS, SCHEMA } = require('chord-synth');
const fs = require('fs');

// Render a WAV buffer
const wav = renderJob({
  preset: "C G Am/E F",
  bpm: 120,
  instrument: "piano",
  pattern: 1,        // Up
  enablePad: true,
  drumPattern: "poprock"
});

fs.writeFileSync('output.wav', wav);

Agent Interface

Agents should call chord-synth --schema to get the full JSON tool specification:

chord-synth --schema

Returns:

{
  "tool": "chord-synth",
  "description": "Generate chord progression WAV files...",
  "input_schema": {
    "type": "object",
    "required": ["preset"],
    "properties": {
      "preset": { "type": "string", "description": "Named preset or custom chords..." },
      "bpm": { "type": "integer", "default": 120 },
      "instrument": { "type": "string", "enum": ["piano","guitar","violin",...] },
      ...
    }
  },
  "examples": [...]
}

List all available options:

chord-synth --list

Parameters

| Parameter | Type | Default | Description | |-----------|------|---------|-------------| | preset | string | required | Named preset ("I-V-vi-IV (Pop)") or custom chords ("C G Am/E F") | | bpm | int | 120 | Tempo | | transpose | int | 0 | Semitones (-11 to +11) | | pattern | int | 1 | Arp pattern index (see below) | | rate | string | "1/8" | Note rate: 1/1 1/2 1/4 1/8 1/16 1/32 (add T for triplet) | | instrument | string | "piano" | piano guitar violin flute clarinet cello bass | | octaveRange | int | 1 | 1-4 octave span | | baseOctave | int | 3 | Starting MIDI octave | | velocity | int | 90 | MIDI velocity 1-127 | | swing | float | 0.5 | 0.5=straight, 0.66=medium, 0.75=heavy | | loops | int | 2 | Progression repetitions | | enablePad | bool | true | Sustained pad chord track | | padOctave | int | 4 | Pad voicing octave | | padVolume | float | 0.12 | Pad volume (0.0-0.3) | | enableBass | bool | true | Auto bass (slash chords set bass note) | | enableDrums | bool | true | Drum track | | drumPattern | string | "poprock" | See drum patterns below | | reverbMix | float | 0.18 | Reverb amount (0.0-0.5) |

Named Presets

| Category | Presets | |----------|---------| | Pop/Rock | I-V-vi-IV (Pop), I-vi-IV-V (50s), vi-IV-I-V (Sad), I-IV-V-IV (Rock), I-V-vi-iii-IV (Canon) | | Jazz | ii-V-I (Jazz), I-vi-ii-V (Jazz Turnaround), iii-vi-ii-V (Coltrane), Autumn Leaves, So What, Steely Dan | | Neo-Soul/R&B | Neo-Soul I, Neo-Soul II, R&B Smooth | | Blues | 12-Bar Blues, Minor Blues | | Latin | Bossa Nova, Girl from Ipanema, Andalusian Cadence, Royal Road (JP) | | Modal/Ambient | Dorian Vamp, Lydian Float, Ambient Pads | | EDM | EDM Anthem, Trance, House | | Classic | Pachelbel Canon, Gospel |

Or use any custom chord string: "Fmaj7 Em7 Dm9 Cmaj7", "Am | Dm/F | E7 | Am", etc.

Arp Patterns

| Index | Name | Index | Name | |-------|------|-------|------| | 0 | Chord (Block) | 11 | Pinky-Thumb | | 1 | Up | 12 | Thumb-Pinky | | 2 | Down | 13 | 1-3-5-3 | | 3 | Up-Down | 14 | 1-5-3-5 | | 4 | Down-Up | 15 | 1-5-8-5 | | 5 | Up-Down (No Repeat) | 16 | 1-3-5-8-5-3 | | 6 | Down-Up (No Repeat) | 17 | Alberti Bass | | 7 | Random | 18 | Stride | | 8 | Random Walk | 19 | Broken 3rds | | 9 | Outside-In | 20 | Pedal Tone | | 10 | Inside-Out | 21 | Alternating Bass |

Drum Patterns

8beat 16beat poprock acousticpop bossanova swing funk rnb waltz arpeggio none

Chord Notation

Roots: C C# Db D D# Eb E F F# Gb G G# Ab A A# Bb B

Qualities: (major) m 7 maj7 m7 dim aug sus2 sus4 9 m9 maj9 11 m11 13 6 m6 dim7 m7b5 add9 5 power

Slash chords: Am/E (Am chord, E bass note), C/G, Dm7/A

Separator: spaces or | both work. C G Am F = C | G | Am | F

Output

WAV PCM 16-bit mono 44100 Hz. Compatible with all DAWs, audio players, and audio processing tools.

License

MIT