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Music Theory Chord Speller
x402
Music Theory Chord Speller is a paid API for AI agents from music-theory.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).
Spells a chord from its symbol (e.g. Cmaj7, F#m7b5, Dsus4, C/E) returning notes, intervals, semitones from root, and MIDI numbers.
Price / call$0.02
Success—
StatusUnknown
How this service works
Spell a chord from its symbol (Cmaj7, F#m7b5, G7b9, Dsus4, C/E): notes, intervals, semitones and MIDI numbers.
Output
Returns a structured object with the chord symbol, root note, bass note, quality, inversion, array of note names (e.g. ['C','E','G','B']), interval names (e.g. ['P1','M3','P5','M7']), semitones from root (e.g. [0,4,7,11]), MIDI numbers at octave 4, and any chord modifications. Also includes a summary string and degraded/error flags.
Example use cases
Chord voicing for MIDI composition
“I'm programming a MIDI sequence and need the exact MIDI note numbers for a G7b9 chord rooted at octave 4 — what notes does that chord contain?”
Music education chord explanation
“Can you spell out the Bbmaj7 chord for my student — show the note names, the intervals from the root, and the semitone distances?”
Figuring out a slash chord
“What notes are actually in a C/E chord? I want to understand the inversion and which note is in the bass.”
Technical details
Endpoint
GEThttps://music-theory.x402tookit.com/chord?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need a programmatic, structured breakdown of a chord from its symbol — including exact note names, interval qualities, semitone distances, and MIDI numbers. Prefer it over scale or key endpoints when the user asks specifically about chord spelling, voicing, or MIDI note content. It handles slash chords (inversions), suspended chords, added-note chords, and complex jazz extensions like m7b5 and 7b9.
Side effects
- Unrecognized or malformed chord symbol returns error reasons array explaining what could not be parsed
- Highly ambiguous or non-standard chord symbols may yield degraded:true with best-effort results
- Missing 'symbol' query parameter returns a validation error
- Extremely unusual extensions or alterations not in the chord library may not resolve correctly
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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