Frequency to nearest note API

Maps any frequency in Hz to the nearest note name and MIDI number and reports the cents deviation (sharp/flat) from in-tune — the core of a pitch/tuner read-out. Answers 'What note is 445 Hz?', 'How many cents flat is 438 Hz from A4?'.

Price$0.04per request

MethodPOST

Route/v1/music/frequency-note

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

musicfrequencytunerpitch-detectioncentsnoteintonationhzaudio

API URLhttps://x402.hexl.dev/v1/music/frequency-note

Integration docs

Example request

{
  "frequency": 445
}

Example response

{
  "frequency": 445,
  "a4Reference": 440,
  "nearestNote": "A4",
  "midi": 69,
  "exactFrequency": 440,
  "centsDeviation": 19.562,
  "inTune": false,
  "direction": "sharp",
  "interpretation": "445 Hz is A4 +19.562 cents"
}

Input schema

{
  "type": "object",
  "required": [
    "frequency"
  ],
  "properties": {
    "frequency": {
      "type": "number",
      "examples": [
        445,
        261.63
      ]
    },
    "a4": {
      "type": "number",
      "examples": [
        440
      ]
    },
    "preferFlats": {
      "type": "boolean"
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}