Deterministic music theory MCP server + REST API for AI builders — analyze chords, roman-numeral analysis, voicings, reharmonization, and conduct
Most developer tooling work still happens through a UI a human drives. Thiri MCP server moves it into the conversation instead. Deterministic music theory MCP server + REST API for AI builders — analyze chords, roman-numeral analysis, voicings, reharmonization, and conduct, 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.
The server publishes 5 tools. What each one is for:
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 recommendationsgenerate_voicing — Instrument-ready voicings (rootless/bill_evans, shell, triad, pad, guide-tones, drop-2/3); pass previousNotes for a voice-leading scorereharmonize — Progression reharmonization — 8 techniques: tritone_sub, ii_v_insertion, modal_interchange, diminished_passing, secondary_dominantconduct_band — Natural-language band conduct → lanes + MIDI (hosted MCP v0.3+)Configuration is passed through the environment: THIRI_API_KEY, YOUR_KEY, THIRI_API_URL. Treat anything key-shaped as a real credential — scope it to the minimum the server needs, and rotate it if it ever lands in a shared config.
Because this one is hosted, setup is mostly authentication — you point your client at the endpoint and approve access. Nothing runs on your machine, so there is no runtime to keep patched.
Plenty of developer tooling servers cover similar ground. The differences that matter in practice are scope of access and how much setup stands between you and a working tool call. Thiri's toolset — analyze_chord, resolve_chord, generate_voicing and 2 more — is a fair guide to whether it matches your workflow. It is maintained by bluesrincemedia; worth a glance at recent repository activity before you build anything load-bearing on it.
SyncDev reviews every entry in this directory against the project's own documentation before publishing, and revisits them as servers change.
| 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+) |
{
"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"]
}
}
}Configuration as documented by the project. Restart the client after saving.
| Variable | Description | Required |
|---|---|---|
| THIRI_API_KEY | Credential the server authenticates with. | Yes |
| YOUR_KEY | Credential the server authenticates with. | Yes |
| THIRI_API_URL | Endpoint or connection string the server talks to. | Yes |
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