maia-util/es6/guess_morphetic.js

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

import guess_morphetic_in_c_major from './guess_morphetic_in_c_major'

const fifth_steps_lookup_array = [
  // Major keys.
  [[-6, 0], 6, 4], [[-5, 0], -1, -1],
  [[-4, 0], 4, 2], [[-3, 0], -3, -2],
  [[-2, 0], 2, 1], [[-1, 0], -5, -3],
  [[0, 0], 0, 0], [[1, 0], 5, 3],
  [[2, 0], -2, -1], [[3, 0], 3, 2],
  [[4, 0], -4, -2], [[5, 0], 1, 1],
  [[6, 0], -6, -3],
  // Minor keys.
  [[-3, 5], 6, 4], [[-2, 5], -1, -1],
  [[-1, 5], 4, 2], [[0, 5], -3, -2],
  [[1, 5], 2, 1], [[2, 5], -5, -3],
  [[3, 5], 0, 0], [[4, 5], 5, 3],
  [[5, 5], -2, -1], [[6, 5], 3, 2],
  [[-6, 5], 3, 2], [[7, 5], -4, -2],
  [[-5, 5], -4, -2], [[8, 5], 1, 1],
  [[-4, 5], 1, 1], [[9, 5], -6, -3]
];
export default function guess_morphetic(mnn, fifth_steps, mode){
  // Tom Collins 15/10/2014.
  // In
  // mnn Integer mandatory
  // fifth_steps Integer mandatory
  // mode Integer mandatory
  // This function takes a MIDI note number and a key (represented by steps on
  // the circle of fiths, and mode). It attempts to guess the corresponding
  // morphetic pitch number, given the key.

  var fifth_steps_idx = 0;
  var n = fifth_steps_lookup_array.length;
  var i = 0;
  while (i < n){
    if (fifth_steps == fifth_steps_lookup_array[i][0][0] &&
        mode == fifth_steps_lookup_array[i][0][1]){
      fifth_steps_idx = i;
      i = n - 1;
    }
    i=i+1;
  }
  var trans = fifth_steps_lookup_array[fifth_steps_idx].slice(1);
  var z = mnn + trans[0];
  var w = guess_morphetic_in_c_major(z);
  var a = w - trans[1];
  return a;
};