Around 1963 Gunther Schuller visited the University of Iowa for some event and joined a "music appreciation" class I attended. His presentation was about "third stream".
After the class he stayed around for discussion with the class. I mentioned John Lewis's "European Windows" and he said something like "Lewis is a friend, but not a real composer". At least that is my ancient memory.
Horenstein's recording of the 3rd symphony (1970) sent me on a Simpson jag. I now have 19 cds and 4 lps including a 10" HMV with Boult conducting the 1st symphony
This arrived in the mail today - from Bobby Bradford! In addition to Bobby the cast includes Henry Franklin, Tina Raymond, Don Preston, Vinny Golia, Chuck Manning and William Roper.