note-to-frequency/es/index.js

🎼 converts a note (scientific pitch notation) to a frequency

import validateNote from 'validate-note';

import getPosition from './lib/getPosition';

export default (function (note) {
  var _ref = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {},
      _ref$base = _ref.base,
      base = _ref$base === undefined ? 440 : _ref$base,
      _ref$maxOctave = _ref.maxOctave,
      maxOctave = _ref$maxOctave === undefined ? 8 : _ref$maxOctave;

  var _validateNote = validateNote(note, {
    flatToSharp: true,
    maxOctave: maxOctave,
    octave: true
  }),
      letter = _validateNote.letter,
      octave = _validateNote.octave,
      signature = _validateNote.signature;

  var pos = getPosition(letter, octave, signature);
  var basePos = getPosition('A', 4);
  var diff = pos - basePos;

  var a = Math.pow(2, 1 / 12);
  return Math.round(base * Math.pow(a, diff) * 100) / 100;
});