Just thinking aloud...I wonder how many obscurities actually exist of this stuff. I guess I'm thinking of 70s LA music as being fed by a similar situation as 70s Hollywood. If you've read Easy Riders and Raging Bulls, you might catch my drift. Basically, in the late 60s/early 70s the film industry had no idea what to do in terms of maintaining sales, so they brought in these young hipsters and threw money at all sorts of projects that would have been considered to out there half a decade earlier. I'm suggesting this because it seems that the interesting feature of this music is that it was almost all released by major labels because major labels seemed willing to release this music at the time. In other words, is it possible that through some alignment of the stars that a most of the people in this scene were able to get this music out and available so that it was never totally obscure?
I can think of a few exceptions of forgotten records like Linda Perhacs (that was on Kapp, not a tiny label), but are there truly many others?
As an amusing aside, I tried pushing the David Crosby record on a friend of mine and it's a really tough sell. I had to preface the whole discussion with, "you have to get past the cover, the album name and the David Crosby."