🎷 THIRI Chord Intelligence — MCP Server

Give your AI real music theory. THIRI is the deterministic music theory MCP server + API for AI builders — it lets Claude, Cursor, or any MCP agent analyze chords, run roman-numeral analysis, generate voicings, and reharmonize progressions with answers that are *computed, not guessed*.

LLMs hallucinate music theory: wrong notes, fake roman numerals, voicings that don't voice-lead. THIRI is a deterministic engine (pitch-class-set theory over ℤ/12) behind a hosted API — so `C7sus4` keeps its suspension, `Caug` spells `C E G#`, and "Coltrane changes on Dm7 G7 Cmaj7" returns `Cmaj7 Ab7 Abmaj7 E7`, every time.

Downstream of Suno / Udio or any generator? Wrap the output and get a correct chord chart your agent can trust. And unlike `tonal.js` or `music21`, THIRI is hosted and agent-native (no install, any language) — and it *reharmonizes* and *voice-leads*, not just looks chords up.

> ⭐ If this is useful, star the repo — it helps other musicians and agent builders find it.

> 👥 Join the First 55 AI Music Builders: Want elevated rate limits (300 req/min), direct founder support, and early access to upcoming tools? Join our developer community on **Skool — Blues People AI**.

Musicians: 2-minute setup (no code)

1. Get a free key at **build.thiri.ai/developers**

2. In Claude: Settings → Connectors → Add custom connector → URL `https://mcp.thiri.ai/mcp` → paste your `sk_live_` key

3. Ask Claude: *"Reharmonize Dm7 G7 Cmaj7 with Coltrane changes."*

That's it — no install, no config file. Builders: full install options (Claude Code, Desktop config, raw HTTP) are below.

What you can ask

> *"Analyze Dm7b5 in C."* → `iiø7`, half-diminished, borrowed predominant, + scale options

> *"What notes are in C7sus4?"* → `C F G Bb` (the suspension survives)

> *"Give me a rootless Cmaj7 voicing, then voice-lead into Dm7."* → voicings + a voice-leading score

> *"Reharmonize Dm7 G7 Cmaj7 with Coltrane changes."* → `Cmaj7 Ab7 Abmaj7 E7`

Tools

> Runs on the v2 grid engine — correct sus chords, real triads, enharmonic spelling, all altered dominants — with request timeouts, quota reporting, and structured errors.

Conductor & composition companions (Desktop only)

For hear-it agent loops (conduct → server-side render → WAV through your speakers), add a second local server alongside hosted theory tools:

{
  "mcpServers": {
    "thiri": {
      "command": "npx",
      "args": ["-y", "@bluesprincemedia/thiri-mcp"],
      "env": { "THIRI_API_KEY": "sk_live_your_key" }
    },
    "thiri-conductor": {
      "command": "npx",
      "args": ["-y", "@bluesprincemedia/thiri-mcp", "thiri-conductor-mcp"],
      "env": { "THIRI_API_KEY": "sk_live_your_key" }
    },
    "thiri-composition": {
      "command": "npx",
      "args": ["-y", "@bluesprincemedia/thiri-mcp", "thiri-composition-mcp"]
    }
  }
}

Rendering runs server-side as of v0.5.0 — no Csound install needed. Proof: `npm run test:conductor` · live docs: build.thiri.ai/lab/conductor-mcp · agent recipes.

Conductor Agent (vibe compose)

End-to-end persona for local vibe composition — skill, CLI, and Band dashboard panel:

Dual MCP config above + `mapConductResultToStudioModules` after each `conduct_band`. Last CLI render writes `~/.thiri/conductor-last.json` (local only, not committed).

Flagship agent recipe (analyze → conduct → render → critique)

Paste in order after dual MCP config above:

1. Analyze — *"Analyze Dm7 G7 Cmaj7 in key C with analyze_chord; summarize roman numerals and tension."*

2. Conduct — *"conduct_band: warm Rhodes pad, walking bass, brush drums, 8 bars medium swing in C."*

3. Render — *"render_audio from the conduct result at tempo 120."*

4. Critique — *"play_audio; critique voice-leading and register balance; suggest one revision."*

Full prompts: build.thiri.ai/lab/agent-recipes

Hosted vs local boundary

Install

Get a free key at **build.thiri.ai/developers**, then pick a path:

Claude Desktop / web / mobile — hosted (one-click custom connector, nothing to install):

Settings → Connectors → Add custom connector → URL `https://mcp.thiri.ai/mcp` → paste your `sk_live_` key on the consent page. Same 5 tools, same key, same quota — no config file, no `npx`.

Claude Code (one line):

claude mcp add thiri --env THIRI_API_KEY=sk_live_your_key -- npx -y @bluesprincemedia/thiri-mcp

Claude Desktop (`claude_desktop_config.json`):

{
  "mcpServers": {
    "thiri": {
      "command": "npx",
      "args": ["-y", "@bluesprincemedia/thiri-mcp"],
      "env": { "THIRI_API_KEY": "sk_live_your_key" }
    }
  }
}

Prefer raw HTTP? (no MCP needed)

The same engine is a plain REST API:

curl -X POST https://chords.thiri.ai/v2/analyze \
  -H "Authorization: Bearer YOUR_KEY" -H "content-type: application/json" \
  -d '{"chord":"Dm7b5","key":"C"}'

Five endpoints: `/v2/analyze`, `/v2/resolve`, `/v2/voicing`, `/v2/reharmonize`, `/v2/conduct`. See `openapi.yaml`.

Environment variables

Development

npm install && npm run build && npm start

License

PolyForm Noncommercial 1.0.0 — © 2026 Blues Prince Media. Free for personal,

research, and noncommercial use; commercial use requires a license

(dennison@bluesprincemedia.com). See `LICENSE`. Versions published at or

before v0.5.0 remain under the MIT/PolyForm dual license they shipped with.

> As of v0.5.0 the composition engine and Csound renderer run server-side behind

> the hosted API (`POST /v2/compose`, `POST /v2/render`); their source no longer

> ships in this package.