Is their a term for the style of movie musical(and broadway) that was prevalent through the late 60s- to the early 80s. Musicals like Rocky Horror,Xanadu,The Apple,Can't Stop the Music, Sgt. Pepper's Lonely Hearts Club ,Band on the Road and to some extent Starlight Express,The Wiz.
What I call them are Acid musicals, A campy and avant grade musical typically with a rock soundtrack that has lose plot, abstract characters, and feel like they were written on acid.
I would try asking Ethan Mordden on Twitter or his blog Cultural Advantages. If anyone knew it would be him. I've read his book about '70s musicals but I can't recall him offering a name for them.
I've not head any specific term, but you're right that it is a definite subgenre. I'd add "Phantom Of The Paradise", "Beyond The Valley Of The Dolls", "Tommy", "Shock Treatment", "Head" - I've never seen "200 Motels" but it seems like it would fit. It could definitely be a fun subject for a book/documentary of some sort. It seems like "Magical Mystery Tour" on TV would be an early example.
I also think it's a genre where you either totally buy into it or you want nothing whatsoever to do with it, and I can respect that.