"HPSCHD" (1969), a gargantuan and long-running multimedia work made in collaboration with Lejaren Hiller, incorporated the mass superimposition of seven harpsichords playing chance-determined excerpts from the works of Cage, Hiller, and a potted history of canonical classics, with 52 tapes of computer-generated sounds, 6,400 slides of designs, many supplied by NASA, and shown from sixty-four slide projectors, with 40 motion-picture films.The piece was initially rendered in a five-hour performance at the University of Illinois in 1969, in which the audience arrived after the piece had begun and left before it ended, wandering freely around the auditorium in the time for which they were there.