I was actually at that Art Rock Festival too, but I managed to miss Jim O'Rourke's performance!
Anyway, he also picked a few films there that were shown in between performances. In case you're interested, they were:
Outer Space (Peter Tscherkassy)
Invocation of my Demon Brother (Kenneth Anger)
Antithese (Mauricio Kagel)
Straight and Narrow (Tony Conrad)
Emperor Tomato Ketchup (Shuji Terayama)