An exercise in randomly generated "Radiohead chord" sequences

radiohead-chords.alda

# Ben Levin's "Radiohead Chord Generator" video:
#   https://www.youtube.com/watch?v=iYU_2hfFPM0

# Rules:
#
# From a MAJOR chord (e.g. C), you can:
#   - move to the parallel minor (Cm)
#   - move down to the relative minor (Am)
#   - move up 1/2 step to a minor chord (Dbm)

# From a MINOR chord (e.g. Cm), you can:
#   - move to the parallel major (C)
#   - move up to the relative major (Eb)
#   - move down 1/2 step to a major chord (B)

# Exercise:
#   - randomly generate the starting chord
#   - randomly generate 7 numbers from 1-3 inclusive
#   - let the 7 numbers determine the path to take
#   - boom, radiohead chord progression

(tempo! 90)

guitar:
  [
    # progression 1
    [
      # Gm - Gb - Ebm - Eb
      o3 g2/>d/g/b-/>d   | o3 g-/>d-/g-/b-/>d- |
      o3 e-/b-/>e-/g-/b- | o3 e-/b-/>e-/g/b-   |

      # Cm - B - Bm - D
      o3 c/g/>c/e-/g   | o2 b/>f+/b/>d+/f+ |
      o2 b/>f+/b/>d/f+ | o3 d/a/>d/f+/a    |
    ] *2

    # progression 2
    [
      # Eb - Em - G - Em
      o3 e-/b-/>e-/g/b- | o3 e/b/>e/g/b |
      o3 g/>d/g/b/>d    | o3 e/b/>e/g/b |
      # Eb - Em - E - Fm
      o3 e-/b-/>e-/g/b- | o3 e/b/>e/g/b   |
      o3 e/b/>e/g+/b    | o3 f/>c/f/a-/>c |
    ] *2
  ] *2