From SPCodex, The Smashing Pumpkins wiki
Mark Ignoffo is a producer and engineer who worked with The Smashing Pumpkins during their sessions at Reel Time Studios in the late 1980s. He played a synthesized organ on the original 1989 recording of "Rhinoceros". Sometime after the sessions concluded, Ignoffo moved his studio to Florida.[1]
As the story goes, Ignoffo was talking to a musician who insisted he meet an "incredible guitar player" named Billy Corgan, and that's how the collaboration began. The Pumpkins and Ignoffo worked together for about a year. In an interview with SPFreaks, Ignoffo said "I think to this day that [Corgan's] amp was one of the loudest I ever recorded in the studio".[1]