note-to-frequency/es/lib/getPosition.js

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

import notes from '../data/notes';

export default (function (letter, octave) {
  var signature = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : '';

  return octave * notes.length + notes.indexOf('' + letter + signature) + 1;
});