Function getChordDegrees

src/progression.ts:12–28

(mode: string)

 * @return {Array} e.g.['I', 'ii', 'iii', 'IV', 'V', 'vi', 'vii°']
 */
export const getChordDegrees = (mode: string): string[] => {
  const theRomans: NVP<string[]> = {
    ionian: ['I', 'ii', 'iii', 'IV', 'V', 'vi', 'vii°'],
    dorian: ['i', 'ii', 'III', 'IV', 'v', 'vi°', 'VII'],
    phrygian: ['i', 'II', 'III', 'iv', 'v°', 'VI', 'vii'],
    lydian: ['I', 'II', 'iii', 'iv°', 'V', 'vi', 'vii'],
    mixolydian: ['I', 'ii', 'iii°', 'IV', 'v', 'vi', 'VII'],
    aeolian: ['i', 'ii°', 'III', 'iv', 'v', 'VI', 'VII'],
    locrian: ['i°', 'II', 'iii', 'iv', 'V', 'VI', 'vii'],
    'melodic minor': ['i', 'ii', 'III+', 'IV', 'V', 'vi°', 'vii°'],
    'harmonic minor': ['i', 'ii°', 'III+', 'iv', 'V', 'VI', 'vii°'],
  };
  theRomans.major = theRomans.ionian;
  theRomans.minor = theRomans.aeolian;

  return theRomans[mode] || [];
};

const idxByDegree: NVP<number> = {
  i: 0,