Sonic Pi Chords 4.0 with modal interchange, secondary dominants, inversions, augmenteds and secondary diminisheds

Sonic Pi Chords 4.0

# MIDI Chord generation
# Now with modal interchange, secondary dominants,
# inversions, augmenteds and secondary diminished
#

define :oneChord do | tonic, mode, deg |
  majorKeyTriads = [:M,:m,:m,:M,:M,:m,:dim]
  minorKeyTriads = [:m,:dim,:M,:m,:m,:M,:M]
  majorKey7s = [:M7,:m7,:m7,:M7,:dom7,:m7,:halfdiminished]
  minorKey7s = [:m7,:halfdiminished,:M7,:m7,:m7,:M7,:dom7]
  
  # First test if deg is actually an array.
  # Because if it is, this is a more complex chord item
  if deg.class == Array then
    # Representation here is [chord-deg, inversion]
    # chord-deg is understood as degree to calculate chord,
    # inversion is 1 (first inversion), 2 (2nd inversion),
    # -1 (first inversion and drop an octave
    # -2 (second inversion and drop an octave)
    
    t,m,c = oneChord(tonic,mode,deg[0])
    
    case deg[1]
    when 0
      newChord = c
    when 1
      newChord = c[1..10]+[c[0]+12]
    when 2
      newChord = c[2..10]+[c[0]+12]+[c[1]+12]
    when 3
      newChord = c[3..10]+[c[0]+12]+[c[1]+12]+[c[2]+12]
      
    when -1
      newChord = (c[1..10]+[c[0]+12]).map {|n| n-12 }
    when -2
      newChord = (c[2..10]+[c[0]+12]+[c[1]+12]).map {|n| n - 12}
    when -3
      newChord = (c[3..10]+[c[0]+12]+[c[1]+12]+[c[2]+12]).map {|n| n - 12}
      
    else
      newChord = c
    end
    return [t,m,newChord]
  end
  
  
  # Modal interchange (negative numbers major <-> minor)
  if deg < 0 then
    return oneChord(tonic,(mode=="major") ? "minor" : "major",-deg)
  end
  
  case deg
  when 1..7 # Simple Triads
    root = degree(deg,tonic,mode)
    lookup = (mode == "major") ? majorKeyTriads : minorKeyTriads
    theChord = chord(root,lookup[deg-1])
  when 71..77 # Seventh Chords
    deg = deg - 70
    root = degree(deg,tonic,mode)
    lookup = (mode == "major") ? majorKey7s : minorKey7s
    theChord = chord(root,lookup[deg-1])
  when 21..27 # Secondary dominants
    deg = deg - 20
    original_root = degree(deg,tonic,mode)
    root = degree(5,original_root,mode)
    theChord = chord(root,:dom7)
    tonic = root
  when 41..47 # augmented (built out of intervals of 4)
    deg = deg - 40
    root = degree(deg,tonic,mode)
    theChord = [root,root+4,root+8]
  when 61..67 # Secondary diminished.(1 below 7)
    # Diminished 7ths half-step below the chord
    deg = deg - 60
    croot = degree(deg,tonic,mode)
    root = croot -1 # half step down
    theChord = chord(root,:dim7)
    tonic = root
  end
  return [tonic,mode,theChord]
end

define :chordSeq do | tonic, mode, degs |
  cs = []
  degs.each { | deg |
    xs = oneChord(tonic,mode,deg)
    cs.append(xs)
  }
  cs
end