It is too bad I was not old enough to be in the loop back then. All of these tunes had lead sheets deposited for copyright. I had a bunch of copyright deposits pulled in the 90s for many composers and they are now collected in boxes, accessible to researchers in the Music Division at the Library of Congress. It is not advertised on their website, however.
This is the same source used for many of the unrecorded pieces that the Herbie Nichols Project premiered.
Now, the Nichols family found more music in a trunk, and Ben Allison just recorded 6 of them.
Bertrand.