It would be very instructive to produce a clear visualisation of the
harmonic variations he uses in each chorus, so I have dropped the
notes of the solo from the .ly file, leaving only the chords, rendered
in landscape, with all the choruses vertically stacked on top of each
other, one per line. This should allow easy visual comparison of any
part of the 12-bar progression simply by scanning vertically at that
point within the progression. However this vertical scan only works
effectively if all the choruses are vertically aligned, hence the need
for proportional spacing.