Interesting!
I think the greatest progressive piece of music in history is "A day in the life" by the Beatles. What's that, 5 chord verse, orchestra run, bompa Macca stuff, aahh, 5 chord verse again, orchestra run, piano hit (which we ripped off!) the end! Nothing technical there. The word" progressive" I think should be used in the true meaning of the word, not to describe a whole genre. Altho' I believe I'm the only one who thinks so.
Come to think of it..."Tomorrow never knows"..the whole song is in D, same (great) beat throughout...for 1966 I'd say that song was pretty fucking progressive! Hell, it still is today!
Cheers people
Mike