Transpose note by semitones API

Transposes a note up or down a given number of semitones and returns the new note name, MIDI number and frequency for both pitches, choosing flat spellings on descent. Answers 'What is C4 up a perfect fifth?', 'Transpose A4 down an octave.'.

Price$0.02per request

MethodPOST

Route/v1/music/transpose

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

musictransposesemitoneintervalpitch-shiftnotemidifrequencyaudio

API URLhttps://x402.hexl.dev/v1/music/transpose

Integration docs

Example request

{
  "note": "C4",
  "semitones": 7
}

Example response

{
  "inputNote": "C4",
  "semitones": 7,
  "transposedNote": "G4",
  "inputMidi": 60,
  "transposedMidi": 67,
  "inputFrequency": 261.6256,
  "transposedFrequency": 391.9954,
  "direction": "up"
}

Input schema

{
  "type": "object",
  "required": [
    "note",
    "semitones"
  ],
  "properties": {
    "note": {
      "type": "string",
      "examples": [
        "C4"
      ]
    },
    "semitones": {
      "type": "number",
      "examples": [
        7,
        -12
      ]
    },
    "a4": {
      "type": "number"
    },
    "preferFlats": {
      "type": "boolean"
    }
  }
}

Output schema

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