PlayByKey Music Theory

PlayByKey Music Theory runs locally from a Node.js package published to the npm registry: @playbykey/theory-mcp version 1.6.0. It speaks MCP over stdio, so the client starts it as a program and talks to it through standard input and output. It needs Node.js; clients usually start it with npx — the usual command is npx -y @playbykey/theory-mcp@1.6.0.

In the mcpServers JSON format that many desktop and editor MCP clients read, the entry looks like this (placeholders in angle brackets):

{
  "mcpServers": {
    "theory-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@playbykey/theory-mcp@1.6.0"
      ]
    }
  }
}

Derived from the registry entry, not tested here. What the server does, and on what terms, is set by its publisher; check its repository or website before giving it access to your accounts or files. How to add an MCP server to an assistant · Before you connect