@playbykey/theory-mcp
An MCP server exposing @playbykey/theory as AI-callable music theory tools. Compute chords, scales, progressions, transpositions, and MIDI/frequency conversions instead of having your AI assistant guess at music theory from training data.
README
<a href="https://playbykey.com"> <picture> <source media="(prefers-color-scheme: dark)" srcset="assets/logo-dark.svg" /> <img src="assets/logo-light.svg" alt="PlayByKey" width="220" height="42" /> </picture> </a>
Developer Tools
Developer-facing packages for PlayByKey. The first shipped package is @playbykey/theory, a zero-dependency TypeScript music theory engine for scales, modes, intervals, key relationships, and note display maps.
- npm: npmjs.com/package/@playbykey/theory
- Documentation: theory-engine.docs.playbykey.com - interactive playgrounds
- Changelog: GitHub Releases
Install
npm install @playbykey/theory
pnpm add @playbykey/theory
yarn add @playbykey/theory
bun add @playbykey/theory
Quickstart and API examples: packages/theory/README.md
Why @playbykey/theory
- Foundation music theory engine: music theory as code. Modes, keys, intervals, and scale relationships resolved deterministically; one source of truth every app, notation tool, or AI agent can build on.
- Zero dependencies: no transitive baggage; safe for agents, edge runtimes, and tight bundles
- TypeScript-first: strict types exported alongside every function, no
any - Agent-ready: copy-paste LLM context prompt and interactive docs
- Sharps-only notation: one canonical spelling per note (
C#, notDb) keeps theNotetype safe and unambiguous. Flats are fully supported for both input (parseNote/parseNoteTokenacceptDb,Eb,Gb,Ab,Bb) and output (getFlats/getEnharmonicLabels), without extendingNoteitself.
Packages
| Package | Description | Links |
|---|---|---|
@playbykey/theory |
Music theory engine (Music Theory Engine on the docs site) | npm · docs · changelog |
@playbykey/theory-mcp |
MCP server that exposes the theory engine as AI-callable tools | npm · README |
theory-docs |
Starlight documentation site (private workspace package) | live site · README |
License
MIT for the repository tooling and @playbykey/theory. See LICENSE.
Individual packages may declare their own license in their package.json.
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