BluesPrince/thiri-mcp

**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**.
Musicians: 2-minute setup (no code)
1. Get a free key at **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
| Tool | What it does |
|------|-------------|
| analyze_chord | Chord → root, quality, intervals, roman numeral & harmonic function (secondary dominants, modal-interchange labels) |
| resolve_chord | Chord → spelled notes (enharmonically correct), frequencies, MIDI, scale recommendations |
| generate_voicing | Instrument-ready voicings (rootless/bill_evans, shell, triad, pad, guide-tones, drop-2/3); pass previousNotes for a **voice-leading score**; colorPreferences for explicit tensions |
| reharmonize | Progression reharmonization — 8 techniques: tritone_sub, ii_v_insertion, modal_interchange, diminished_passing, secondary_dominant, chain_of_dominants, coltrane_changes, backdoor (or auto) |
| conduct_band | Natural-language band conduct → lanes + MIDI (hosted MCP v0.3+) |
> 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:
| Bin | Tools |
|-----|-------|
| thiri-conductor-mcp | conduct_band, render_audio (server-side Csound via POST /v2/render), play_audio, search_corpus |