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Music Theory: Frequency to Nearest Note
x402
Music Theory: Frequency to Nearest Note 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).
Converts a frequency in Hz to the nearest musical note, MIDI number, and cents offset, with adjustable A4 reference pitch.
Price / call$0.02
Success—
StatusUnknown
How this service works
Frequency in Hz to the nearest note, MIDI number and offset in cents; adjustable A4 reference; tuner-style result.
Output
Returns the nearest note name (e.g. A4, C#3), MIDI number, fractional MIDI, cents offset from the nearest note, the nearest note's exact frequency in Hz, the A4 reference used, and metadata such as a summary and direction (sharp/flat).
Example use cases
Instrument tuner pitch check
“I'm recording a guitar that's slightly out of tune — the string is ringing at about 329 Hz. What note is that closest to, what's the MIDI number, and how many cents flat or sharp is it?”
Verify synthesizer oscillator pitch
“My synth is outputting 880.5 Hz. Can you tell me the nearest note name using sharps, the MIDI note number, and the cents offset from the true pitch?”
Analyze historical tuning reference
“If I'm working with baroque music tuned to A4 = 415 Hz and I have a frequency of 415 Hz, what note does that correspond to, what's the MIDI number, and what's the cents deviation?”
Technical details
Endpoint
GEThttps://music-theory.x402tookit.com/freq-note?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to identify the musical note, MIDI number, and tuning deviation for a raw frequency value — ideal for tuner apps, pitch analysis, instrument calibration, or translating audio frequency measurements into musical context. Prefer this over a note-to-frequency endpoint when the input is a raw Hz value rather than a note name.
Side effects
- Frequency out of range (below 8 Hz or above 14000 Hz) returns an error
- A4 reference out of allowed range (400–480 Hz) returns a validation error
- Missing required 'hz' query parameter results in a bad request error
- Invalid accidentals value (not 'sharps' or 'flats') may cause unexpected behavior
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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