What is PlayByKey Music Theory?

Chords, scales, progressions, transposition, and MIDI tools for music theory AI agents.

How do I install PlayByKey Music Theory?

Install PlayByKey Music Theory via npm from https://registry.npmjs.org, then add the server config to your MCP client (Claude Desktop, Cursor, or VS Code).

Is PlayByKey Music Theory open source?

Yes, PlayByKey Music Theory is open source under the MIT license. Source code is available at https://github.com/DigitalBrewLLC/playbykey-dev-tools.

What category does PlayByKey Music Theory belong to?

PlayByKey Music Theory is listed under AI & ML MCP servers on MCPFind.

PlayByKey Music Theory — MCP Server for AI & ML

Developer Tools

Packages for PlayByKey - see the table below for what's here.

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
Strictly typed: every function's types exported alongside it, no any
Agent-ready: copy-paste LLM context prompt and interactive docs
Sharps-only notation: one canonical spelling per note (C#, not Db) keeps the Note type safe and unambiguous. Flats are fully supported for both input (parseNote/parseNoteToken accept Db, Eb, Gb, Ab, Bb) and output (getFlats/getEnharmonicLabels), without extending Note itself.

Packages

Package	Description	Links
`@playbykey/theory`	Zero-dependency music theory engine - scales, modes, intervals, chords, progressions, key relationships	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.

Set up in your AI client

AI clientOperating system

Merge this template into ~/Library/Application Support/Claude/claude_desktop_config.json. Keep existing servers. Add any arguments, credentials, and permissions required by the maintainer; this template has not been install-tested.

json

{
  "mcpServers": {
    "com-playbykey-theory-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@playbykey/theory-mcp"
      ]
    }
  }
}

Restart Claude Desktop completely for changes to take effect. Confirm the server appears connected in the client’s tool list, then try a read-only example from its documentation.

Claude Desktop setup reference

Compatible MCP Clients

PlayByKey Music Theory works with any MCP-compatible client. Copy the config snippet from the Configuration section above and add it to the file shown for your client, then restart the application.

Claude Desktop~/Library/Application Support/Claude/claude_desktop_config.jsonRestart Claude Desktop completely for changes to take effect.

Cursor~/.cursor/mcp.jsonRestart Cursor for changes to take effect.

VS Code.vscode/mcp.jsonReload VS Code window for changes to take effect.

Windsurf~/.codeium/windsurf/mcp_config.jsonRestart Windsurf for changes to take effect.

Claude Code.mcp.jsonSave at the project root, then start Claude Code in that project and review the MCP server approval prompt. Keep real credentials out of shared files.

PlayByKey Music Theory