THIRI Chord Intelligence

🎷 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 AI Music Builders: Want elevated rate limits, direct founder support, and early access to upcoming tools? Join our developer community on [Skool — T.H.I.R.I. Builders](https://www.skool.com/thiri-builders-6682/about).

Musicians: 2-minute setup (no code)

1. Get a free key at [build.thiri.ai/keys](https://build.thiri.ai/keys)
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/keys](https://build.thiri.ai/keys), 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`](./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.