I interviewed Zappa about his film 200 Motels. It was back stage at The Rock Pile (really an old Masonic Hall) in Toronto and both The Mothers and most of Blood, Sweat and Tears were present. Both bands were happy to be sharing a bill with another group that included horn players. Zappa began talking about a Chicago band called CTA that also had horn players, saying that if all three band could get a gig together they could do some interesting stuff. He was much more benign towards his audiences that he was with Larry. He talked about how he would get letters from kids who wrote that they were the only freaks in their town and his records made them feel that they were not alone in the world. The biggest negative about the interview for me was that he had a very demeaning attitude toward women and kept talking about "strapping them on".
I once saw the Mothers on a double bill with The Mahavishnu Orchestra in Maple Leaf Gardens.
Ian Underwood played on many of the film recording sessions I attended. From Frank Zappa to Elmer Bernstein.