LONGWOOD — Passersby who peeked through the gym doors at the Casita Maria youth center recently were met by a strange sight.

Mark Bolotin, a visiting Australian artist, stood before a plastic 12-headed creature singing and playing the keyboard. The creature sang along.

Bolotin, 32, and his band were rehearsing for Saturday, when the Lumiphonic Creature Choir will make its Bronx debut.

“It’s an interactive, multimedia, rock-and-roll show,” Bolotin explained, “a true collaboration between the virtual and the real.”