analyze_chord
Parse a chord symbol into its root, quality, intervals, extensions, and harmonic function. When a key is provided, returns the Roman numeral, scale degree, and whether the chord is diatonic.
LABSCO SUMMARY
C7sus4 keeps its suspension, every time.
Models hallucinate music theory in a way that sounds plausible and is not — wrong notes, invented Roman numerals, voicings that lead nowhere. This computes over pitch-class sets instead, so the same question returns the same correct answer, and the voice-leading score is a number rather than a claim.
What it is
A deterministic music theory engine behind a hosted API. It parses a chord symbol into root, quality, intervals and harmonic function, spells the notes enharmonically correctly, generates instrument-ready voicings with a voice-leading score, and reharmonises a progression using named jazz techniques.
What you get
- analyze_chord returns root, quality, intervals, extensions and harmonic function; given a key it adds the Roman numeral, scale degree and whether the chord is diatonic
- resolve_chord returns spelled note names, frequencies in Hz, MIDI numbers and recommended improvisation scales
- generate_voicing produces voicings in a named style — rootless, bill_evans, shell, triad, pad, guide-tones and drop voicings — and scores the voice leading against a previous voicing you pass in
- reharmonize returns one alternative per applicable technique, each with the new progression, the changes and a plain-English explanation; techniques include tritone_sub, ii_v_insertion, modal_interchange, diminished_passing, secondary_dominant, chain_of_dominants, coltrane_changes and backdoor, or auto for everything that applies
- conduct_band arranges a four-piece band from a natural-language prompt and returns tempo and groove, four lanes of note events, a lead sheet and base64 MIDI
- Two companion binaries ship in the same package: thiri-conductor-mcp adds server-side rendering and playback, thiri-composition-mcp adds composition tools
Requirements
Two ways in. Hosted: add https://mcp.thiri.ai/mcp as a custom connector and paste your sk_live_ key — no install. Local: the npm package @bluesprincemedia/thiri-mcp over stdio with THIRI_API_KEY in the environment. Free keys come from build.thiri.ai/developers. The conductor and composition binaries are desktop-only and run alongside the main server; rendering happens server-side, so no local Csound install is needed.
Setup effort
One command plus a key — claude mcp add thiri --env THIRI_API_KEY=<YOUR_THIRI_API_KEY> -- npx -y @bluesprincemedia/thiri-mcp
USE CASES
01
Getting the notes in a chord right
Spelled note names, frequencies and MIDI numbers, with the harmonic reading alongside them.
02
Turning a chord chart into Roman numerals
Give the key and get the numeral, the scale degree and whether the chord is borrowed.
03
Finding a voicing that leads from the last one
Pass the previous voicing and get a scored transition rather than an isolated chord shape.
04
Reharmonising a progression a specific way
Name the technique, or ask for every technique that applies, each with an explanation of what changed.
05
Sketching an arrangement from a description
A natural-language prompt becomes tempo, groove, four instrument lanes, a lead sheet and MIDI.
5 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
conduct_band
Arrange a 4-piece band from a natural-language prompt. Returns conductor tempo/groove, 4 lanes of note events, lead sheet, and base64 MIDI. Browser/client synthesizes audio via Csound; use thiri-conductor-mcp locally to render WAV.
generate_voicing
Generate instrument-ready voicings for a chord in a specified style. Pass previousNotes (or a previousVoicing object) from an earlier result to get a voiceLeadingScore for the transition. Styles: rootless, bill_evans, shell, triad, pad, guide-tones, guide-tone-1, guide-tone-2, both-guide-tones, drop-2, drop-3.
reharmonize
Reharmonize a chord progression using jazz techniques. Returns one alternative per applicable technique, each with the new progression, the changes, and a plain-English explanation. With technique 'auto' (default) it returns every technique that applies. Techniques: tritone_sub, ii_v_insertion, modal_interchange, diminished_passing, secondary_dominant, chain_of_dominants, coltrane_changes, backdoor. (modal_interchange and backdoor require a key.)
resolve_chord
Resolve a chord symbol to spelled note names, frequencies in Hz, MIDI numbers, and recommended improvisation scales.
BEFORE YOU INSTALL
What to know first
Tools you get
5 tools when we connected. The package also ships thiri-conductor-mcp and thiri-composition-mcp, separate servers with their own tools. The hosted connector exposes the same 5.
Requires
- npx on PATH
- THIRI_API_KEY in your environment
CONTEXT COST
Light Standing cost
Rated by the size of the 5 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Server setup
claude mcp add
Claude Code
TERMINAL
claude mcp add thiri --env THIRI_API_KEY=<YOUR_THIRI_API_KEY> -- npx -y @bluesprincemedia/thiri-mcpHosted endpoint
ENDPOINT URL
https://mcp.thiri.ai/mcpAdd this hosted endpoint to your MCP client using the credentials listed under Requirements.
MCP Clients
Claude Desktop — remote
Settings → Connectors → Add custom connector → URL https://mcp.thiri.ai/mcp → paste your sk_live_ key on the consent page
Claude Desktop — npx
CLAUDE DESKTOP — NPX · JSON
{
"mcpServers": {
"thiri": {
"command": "npx",
"args": [
"-y",
"@bluesprincemedia/thiri-mcp"
],
"env": {
"THIRI_API_KEY": "<YOUR_THIRI_API_KEY>"
}
}
}
}Claude Desktop — dual config
CLAUDE DESKTOP — DUAL CONFIG · JSON
{
"mcpServers": {
"thiri": {
"command": "npx",
"args": [
"-y",
"@bluesprincemedia/thiri-mcp"
],
"env": {
"THIRI_API_KEY": "<YOUR_THIRI_API_KEY>"
}
},
"thiri-conductor": {
"command": "npx",
"args": [
"-y",
"-p",
"@bluesprincemedia/thiri-mcp",
"thiri-conductor-mcp"
],
"env": {
"THIRI_API_KEY": "<YOUR_THIRI_API_KEY>"
}
},
"thiri-composition": {
"command": "npx",
"args": [
"-y",
"-p",
"@bluesprincemedia/thiri-mcp",
"thiri-composition-mcp"
]
}
}
}
