{
  "model": "12-tone equal temperament; A4=440Hz. Frequencies are calculated, not piano measurements.",
  "notes": [
    {
      "pitch": "C4",
      "semitones_from_c4": 0,
      "midi": 60,
      "key": "white",
      "frequency_hz": 261.625565
    },
    {
      "pitch": "C♯4/D♭4",
      "semitones_from_c4": 1,
      "midi": 61,
      "key": "black",
      "frequency_hz": 277.182631
    },
    {
      "pitch": "D4",
      "semitones_from_c4": 2,
      "midi": 62,
      "key": "white",
      "frequency_hz": 293.664768
    },
    {
      "pitch": "D♯4/E♭4",
      "semitones_from_c4": 3,
      "midi": 63,
      "key": "black",
      "frequency_hz": 311.126984
    },
    {
      "pitch": "E4",
      "semitones_from_c4": 4,
      "midi": 64,
      "key": "white",
      "frequency_hz": 329.627557
    },
    {
      "pitch": "F4",
      "semitones_from_c4": 5,
      "midi": 65,
      "key": "white",
      "frequency_hz": 349.228231
    },
    {
      "pitch": "F♯4/G♭4",
      "semitones_from_c4": 6,
      "midi": 66,
      "key": "black",
      "frequency_hz": 369.994423
    },
    {
      "pitch": "G4",
      "semitones_from_c4": 7,
      "midi": 67,
      "key": "white",
      "frequency_hz": 391.995436
    },
    {
      "pitch": "G♯4/A♭4",
      "semitones_from_c4": 8,
      "midi": 68,
      "key": "black",
      "frequency_hz": 415.304698
    },
    {
      "pitch": "A4",
      "semitones_from_c4": 9,
      "midi": 69,
      "key": "white",
      "frequency_hz": 440.0
    },
    {
      "pitch": "A♯4/B♭4",
      "semitones_from_c4": 10,
      "midi": 70,
      "key": "black",
      "frequency_hz": 466.163762
    },
    {
      "pitch": "B4",
      "semitones_from_c4": 11,
      "midi": 71,
      "key": "white",
      "frequency_hz": 493.883301
    }
  ],
  "white_key_steps": [
    2,
    2,
    1,
    2,
    2,
    2,
    1
  ],
  "fifth_chain_pitch_classes": [
    5,
    0,
    7,
    2,
    9,
    4,
    11
  ],
  "pure_fifth_ratio": "3/2",
  "tempered_fifth_ratio": 1.4983070768766815,
  "pure_fifth_cents": 701.9550008653874,
  "tempered_fifth_cents": 700,
  "pythagorean_comma_ratio": "531441/524288",
  "pythagorean_comma_cents": 23.460010384649014,
  "pythagorean_c_major_cents": [
    0.0,
    203.910002,
    407.820003,
    498.044999,
    701.955001,
    905.865003,
    1109.775004
  ],
  "whole_tone_example_pitch_classes": [
    0,
    2,
    4,
    6,
    8,
    10
  ],
  "references": [
    "https://www.phys.unsw.edu.au/jw/notes.html",
    "https://www.yamaha.com/en/musical_instrument_guide/piano/play/"
  ],
  "limits": [
    "A displayed frequency is not a measurement. Real piano strings have inharmonicity and may use stretched tuning.",
    "Equal temperament makes enharmonic labels coincide; other tuning systems can distinguish them.",
    "Diagram shows seven white keys plus five black keys, without the next octave C endpoint."
  ],
  "reference_examples": [
    {
      "midi": 67,
      "relative_to_A4_semitones": -2,
      "frequency_hz": 391.995436
    },
    {
      "midi": 68,
      "relative_to_A4_semitones": -1,
      "frequency_hz": 415.304698
    },
    {
      "midi": 69,
      "relative_to_A4_semitones": 0,
      "frequency_hz": 440.0
    },
    {
      "midi": 70,
      "relative_to_A4_semitones": 1,
      "frequency_hz": 466.163762
    },
    {
      "midi": 71,
      "relative_to_A4_semitones": 2,
      "frequency_hz": 493.883301
    },
    {
      "midi": 72,
      "relative_to_A4_semitones": 3,
      "frequency_hz": 523.251131
    },
    {
      "midi": 73,
      "relative_to_A4_semitones": 4,
      "frequency_hz": 554.365262
    }
  ]
}