“Music Box Massacre,” the annual horror-movie marathon presented by Music Box and the Movieside Film Festival, has split into two rival events: “Music Box of Horrors,” which took place last weekend at Music Box, and “The Massacre,” this weekend at the Portage Theater. Screening at the Portage in 35-millimeter, unless otherwise noted: Un Chien Andalou, with live organ accompaniment by Jay Warren (Sat 10/20, noon); Edgar G. Ulmer’s The Black Cat (12:30 PM); The Curse of the Werewolf (1:45 PM); The Conqueror Worm (3:30 PM); the early David Cronenberg short From the Drain (5:15 PM), from a 16-millimeter print; Spider Baby (5:30 PM), with director Jack Hill in person; The Return of the Living Dead, with actress Linnea Quigley in person (7:45 PM); Phantasm II (10 PM); The Captured Bird (11:45 PM); A Nightmare On Elm Street 3: Dream Warriors (Sun 10/21, midnight); the Japanese cult film House (1:45 AM); Nightmares (3:15 AM); John Carpenter’s Prince of Darkness (5 AM); Dead Snow (6:45 AM); Alfred Hitchcock’s Frenzy (8:30 AM); and Halloween II (10:30 AM).