The performance “ONCE. MORE.: ONCE THEN,” 8-11 p.m. Tuesday at Rackham Auditorium, celebrates the 50th anniversary of the founding of the ONCE festival in Ann Arbor, by avant-garde composers Robert Ashley, Gordon Mumma, Roger Reynolds, Donald Scavarda and the late George Cacioppo. Performing will be faculty from the School of Music, Theatre & Dance; the Creative Arts Orchestra; Digital Music Ensemble; and Ann Arbor Improvisation Collective. Sponsored by the University Musical Society. Photo by Donald Scavarda.