pyComputeUkeleleChords

# Compute fingering required for playing chords on a Ukelele
# Mike Kerry - Jan 2024

scale = ["A", "Bb", "B", "C", "C#", "D", "Eb", "E", "F", "F#", "G", "Ab"]
scale += scale

base_notes_open = ["G", "C", "E", "A"]      # Notes that open strings play
base_note_offsets = [10, 3, 7, 0]           # Open string notes relative to A

chords = {"1,5,8": "", "1,5,8,10": "6", "1,5,8,11": "7", "1,5,8,12": "maj7",
          "1,4,8": "m", "1,4,8,10": "m6",  "1,3,8,11": "m7"}

strings = [0, 0, 0, 0]
lastcombo = ""
lastfullkey = ""
high_fret = 4                   # Highest fret wwe want to use
chord_list = []
for off1 in range(high_fret + 1):
    for off2 in range(high_fret + 1):
        for off3 in range(high_fret + 1):
            for off4 in range(high_fret + 1):
                strings[0] = scale[base_note_offsets[0] + off1]
                strings[1] = scale[base_note_offsets[1] + off2]
                strings[2] = scale[base_note_offsets[2] + off3]
                strings[3] = scale[base_note_offsets[3] + off4]

                for first_note in strings:
                    first_note_index = scale.index(first_note)
                    intervals = []      # compute a list of intervals from one string to all strings
                    for second_note in strings:
                        second_note_index = scale.index(second_note)
                        interval = (second_note_index + 12 - first_note_index) % 12
                        intervals.append(interval)
                    intervals = list(set(intervals))        # drop duplicate intervals
                    intervals.sort()                        # e.g. for major we want 1, 5, 8 not 5, 1, 8 etc.
                    interval_key = ""
                    for a in intervals:
                        interval_key += str(a + 1)          # count notes from 1, not 0
                        interval_key += ","
                    interval_key = interval_key[:-1]        # drop the final comma

                    if interval_key in chords:              # Does this set of intervals make any desired chord?
                        combo = f"{off1},{off2},{off3},{off4}"
                        fullkey = f"{first_note}{chords[interval_key]}"
                        if combo == lastcombo and fullkey == lastfullkey:
                            continue            # ignore duplicates
                        lastcombo = combo
                        lastfullkey = fullkey
                        chord_list.append([fullkey, combo])

chord_list.sort()

# Print sorted results
for item in chord_list:
    offsets = item[1]
    offlist = offsets.split(',')
    outline = f"{item[0]: <8} {item[1]: <10} "
    notes = []
    notes_str = ""
    for x, off in enumerate(offlist):
        off = int(off)
        idx = base_note_offsets[x] + off
        notes.append(scale[idx])
        notes_str += scale[idx]
        notes_str += " "
    notes_str += "            "
    outline += notes_str[:12]
    if notes[0] in notes[1:] and item[1][0] != '0':
        outline += "   or  x,"
        outline += item[1][2:]

    print(outline)