Tries to account for chord changes in a Bach Chorale by brute-forcing the 24 unique LPR operations

NRTfinder.py

import music21

# From Hook/Andrew Chung

LRPgroup = ['', 'P', 'LPRP', 'LPR', 'LRL', 'PRPL', 'LRLR', 'RLR', 'LPRPR', 'LRPR', 'PR', 'PRP',
		'R', 'RP', 'LP', 'L', 'LPL', 'PL', 'RL', 'PLR', 'LPR', 'LR', 'PRPR', 'RPR']

LRPCombinations = music21.analysis.neoRiemannian.LRP_combinations

def getCanonicalTransform(source, target):
  for operation in LRPgroup:
    if sorted(target.pitchClasses) == sorted(LRPCombinations(source, operation).pitchClasses):
      return operation

def doAnalysisToChordList(chords):
  analysis = []
  for index in range(len(chords)-1):
    print (("".join(chords[index].pitchNames), "".join(chords[index+1].pitchNames), getCanonicalTransform(chords[index], chords[index+1])))

jsb = music21.corpus.parse('bwv7.7')
reduction = jsb.chordify()

chords = []
for chord in reduction.flat.getElementsByClass('Chord'):
  chords.append(chord.closedPosition(forceOctave=4, inPlace=False))

doAnalysisToChordList(chords)