'Gets a histogram of the how many notes fit into each key.
Returns:
A list of 12 ints, one for each Major key (C Major at index 0 through
B Major at index 11). Each int is the total number of notes that could
fit into that key.'

def get_major_key_histogram(self):

    note_histogram = self.get_note_histogram()
    key_histogram = np.zeros(NOTES_PER_OCTAVE)
    for (note, count) in enumerate(note_histogram):
        key_histogram[NOTE_KEYS[note]] += count
    return key_histogram
