Hi,
It's one of the toughest things in the ProgArchives kindergarten ... to help people understand what an "artistic scene" is in any place of time and history, will always create music, art, and literature ... and it will seem that the rest of the time is ... empty.
So "progressive" has a link to the socio-political thing at the time, and its history, from which a lot of music came, and it's hard explaining to the kiddies that "20th century schizoid" man is not a rock song, but a nasty pointed (and loaded) finger that is no different than "Foreign Son" ... but no .... it's progressive because of the jagged guitar and this and that ... and not its indictment to the madness that was already on television for your delectation!
So, if the CHB has no social-political value, don't blame it on me ... blame it on the times ... they are empty!
it is a tough issue ... but it tells you how much people know, read, and learn ... and USE, in their daily lives!