Alex V. Cook has an interview of Dickie Landry, a founding member of the Philip Glass Ensemble.
I particularly liked the part on helping Glass understand the value of accomplished musicians:
Landry pulls out a picture of one of the early Philip Glass Ensemble rehearsals noting the talented composers in the group but comments, “Philip and them were great composers but not the best technicians. They could play, but they really couldn’t play. We were rehearsing music for changing parts and it was like dee-dee-dee-mistake, dee-dee-dee-mistake. Oh God, I thought, this is like torture. I finally convinced him to get rid of these guys and told him I got some friends coming up to New York City; let’s rehearse with them and see what happens. We can read and play it faster and we can do this.”
Music With Changing Parts - Ph...
Keep in mind the work embedded from lala above is over an hour long.aworks: prior post on music with changing parts