Phillips helped promote the Monterey International Pop Music Festival held June 16 to 18, 1967, in Monterey, California; he performed with the Mamas and the Papas as part of the event as well. The festival was planned in just seven weeks, and was developed as a way to validate rock music as an art form in the way jazz and folk were regarded. It was the first major pop-rock music event in history. He also co-produced the film "Monterey Pop" (1968) with the group's producer Lou Adler.