The answer

PlayByKey Music Theory

Top verified match: it matches your intent, it is the official vendor server, corroborated across multiple registries.

fresh · published 8d ago · verified 2026-08-01tested · static-verifiedsigned passport ✓score 53/100

claude mcp add PlayByKey Music Theory -- npx -y @playbykey/theory-mcp

Runners-up

THIRI Chord Intelligence — Music Theory MCP Servernot yet verified8/100 · weaker match
io.github.asume21/music-theory-mcp35/100 · weaker match
Hooktheory MCP Servernot yet verified13/100 · weaker match