maia-util/es6/guess_morphetic_in_c_major.js

Utility math and music functions supporting various applications by Music Artificial Intelligence Algorithms, Inc.

const midi_residue_lookup_array = [
  [0, 0], [1, 0], [2, 1], [3, 2],
  [4, 2], [5, 3], [6, 3], [7, 4],
  [8, 4], [9, 5], [10, 6], [11, 6]
];

export default function guess_morphetic_in_c_major(mnn){
  // Tom Collins 15/10/2014.
  // In
  // mnn Integer mandatory
  // Out Integer
  // This function takes a MIDI note number as its only argument. It
  // attempts to guess the corresponding morphetic pitch number, assuming
  // a key of or close to C major.

  var octave = Math.floor(mnn/12 - 1);
  var midi_residue = mnn - 12*(octave + 1);

  var midi_residue_idx = 0;
  var n = midi_residue_lookup_array.length;
  var i = 0;
  while (i < n){
    if (midi_residue == midi_residue_lookup_array[i][0]){
      midi_residue_idx = i;
      i = n - 1;
    }
    i=i+1;
  }
  var mpn_residue = midi_residue_lookup_array[midi_residue_idx][1];
  var a = mpn_residue + 7*octave + 32;
  return a;
};