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Thiri MCP

by BluesPrince

Deterministic MCP tools for chord analysis, note resolution, voicing, reharmonization, and four-piece band arrangements.

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Install Thiri MCP

Pick your client, then add it in one click or paste the config.

STDIONode.js
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "bluesprince-thiri-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@bluesprincemedia/thiri-mcp"
      ],
      "env": {
        "THIRI_API_KEY": "YOUR_VALUE_HERE",
        "THIRI_API_URL": "YOUR_VALUE_HERE"
      }
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Values are written into the snippet above so you can paste it as is. They never leave your browser.

Install not yet sandbox-tested— the server itself is confirmed live (we called its tools/list endpoint). The stdio install command is a separate, ongoing check.

Overview

BluesPrince/thiri-mcp MCP server provides deterministic music-theory tools through a hosted API or local npx MCP process. It analyzes chords, resolves notes and MIDI data, generates styled voicings with optional voice-leading scores, and reharmonizes progressions. The server also accepts natural-language band prompts and returns arrangement lanes, a lead sheet, and base64 MIDI. Reach for it when an agent needs computed harmonic results rather than generated guesses.

Use cases

  • Analyze generated chord progressions
  • Resolve chord symbols into MIDI and frequencies
  • Generate voice-led jazz voicings
  • Reharmonize progressions with named techniques
  • Arrange natural-language band prompts

Key features

  • Deterministic chord and Roman-numeral analysis
  • Enharmonic note, frequency, and MIDI resolution
  • Style-based voicing generation
  • Voice-leading transition scores
  • Jazz progression reharmonization
  • Four-piece band arrangement with MIDI output

Tools5

What Thiri MCP lets your agent do. Expand a tool for its parameters.

Verified live~1.0k tokens of context

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked 1d ago

Recent health check succeeded.

7/7 checks healthy over the last 78d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 10d ago via OSV.dev · @bluesprincemedia/thiri-mcp (npm)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars12Stargazers on the source repository.
npm downloads227Package downloads in the last 30 days.
Last commit8d agoMost recent push to the default branch.
Tools exposed5Callable tools this server registers over MCP.
Directory activity4 viewsConfig copies, upvotes, and views on AllMCPs.

How Thiri MCP works

What BluesPrince/thiri-mcp MCP server does

BluesPrince/thiri-mcp MCP server connects an MCP client to THIRI’s hosted music-theory API. Its core operations cover chord-symbol analysis, note and pitch resolution, voicing generation, progression reharmonization, and four-piece band arrangement. Results are structured for agent workflows instead of being limited to prose explanations.

Chord analysis can identify a root, quality, intervals, extensions, harmonic function, Roman numeral, scale degree, and diatonic status when a key is supplied. Resolution adds spelled notes, frequencies in hertz, MIDI numbers, and recommended improvisation scales. This makes the server suitable for checking generated chord charts or extracting usable musical data.

How it works

The MCP tools send requests to the THIRI API. The hosted MCP endpoint is https://mcp.thiri.ai/mcp, while the package can also run through npx @bluesprincemedia/thiri-mcp. Authentication uses a THIRI bearer key. The API base defaults to https://chords.thiri.ai and can be overridden for local development.

generate_voicing accepts a chord and style such as rootless, Bill Evans, shell, triad, pad, guide tones, drop-2, or drop-3. Supplying notes or a previous voicing from an earlier result enables a voice-leading score for the transition. reharmonize can apply techniques including tritone substitution, ii–V insertion, modal interchange, diminished passing chords, secondary dominants, chains of dominants, Coltrane changes, and backdoor movement. Modal interchange and backdoor reharmonization require a key.

conduct_band turns a natural-language arrangement prompt into conductor information, four note-event lanes, a lead sheet, and base64 MIDI. The hosted surface returns the arrangement data but does not render audio. Audio rendering is available through the separate local thiri-conductor-mcp companion, which uses server-side Csound and can produce WAV output.

Setup and configuration

To use the BluesPrince/thiri-mcp MCP server, obtain a key from build.thiri.ai/developers. Claude can connect directly through a custom connector using the hosted MCP URL and the key. For local stdio configuration, run the package with npx and set THIRI_API_KEY in the MCP server environment.

A Claude Code command is:

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

The supported environment variables are:

  • THIRI_API_KEY: bearer token used for API authentication.
  • THIRI_API_URL: optional API base override; it defaults to https://chords.thiri.ai.

The repository also documents a dual local setup for the theory server and thiri-conductor-mcp, plus a composition companion. Those additional processes are needed for local rendering or composition-specific workflows and are separate from the core five-tool MCP surface.

Tools and capabilities

  • analyze_chord: returns harmonic and structural chord information, with key-aware Roman-numeral analysis.
  • resolve_chord: returns enharmonically spelled notes, frequencies, MIDI values, and scale suggestions.
  • generate_voicing: creates instrument-ready voicings and can score transitions against a previous voicing.
  • reharmonize: produces applicable alternatives for a progression with changes and plain-language explanations.
  • conduct_band: creates a four-part arrangement from a natural-language prompt and returns lanes, lead sheet data, and MIDI.

Limitations and notes

The hosted connector does not provide audio rendering; it returns theory results and conduct_band lanes. Use the local conductor companion when a workflow needs server-rendered WAV playback. The API requires a THIRI key, and the README identifies commercial use as requiring a separate license under the PolyForm Noncommercial 1.0.0 terms.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Thiri MCP

BluesPrince/thiri-mcp is an MCP server that connects AI clients to THIRI’s hosted music-theory API. Its main tools analyze and resolve chords, generate voicings, reharmonize progressions, and conduct four-piece band arrangements. Results include harmonic metadata, notes, MIDI values, and structured arrangement data.

Install it with npx by configuring `@bluesprincemedia/thiri-mcp` as an MCP server and setting `THIRI_API_KEY`. Claude Desktop uses an MCP configuration file, while Claude Code supports `claude mcp add`. Claude can also connect to the hosted URL without a local install.

Yes, the README names Cursor as a supported MCP client. Configure Cursor to use the hosted MCP endpoint or the local npx process, and provide `THIRI_API_KEY` when using the authenticated API.

The core hosted MCP surface does not render audio. It returns `conduct_band` lanes, a lead sheet, and base64 MIDI. Use the separate local `thiri-conductor-mcp` companion for server-side Csound rendering and WAV playback.

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