I've started trying to write 8-bar chord progressions that use all the major-scale diatonic chords, plus all the chords from a parallel mode, exactly once. So far I've done major/minor, major/Dorian, and major/Phrygian. It's a pretty entertaining challenge. I figured I'd post them here, in case anyone has suggestions for improvements, or wants to try it themselves.
(I decided the minor tonic is optional, by the way.)
@jtullis, really enjoyed this, especially the Major/Phrygian progression. Have you thought about trying to write some melodies as well?
I hadn't, actually - I'm not particularly skilled with melodies - but I'll give it a shot once I finish the rest of the modes. (Not looking forward to Locrian...)