The Beatles and Jimi Hendrix both experimented with recording guitars (or other instruments) to a reel of analog tape that had been reversed on the tape recorder. Once the part or parts are recorded, the reel was flipped over to play in the correct direction. When the "reverse"-recorded parts were played back, they sounded backward. Famous examples are The Beatles' "Tomorrow Never Knows" and "Within You Without You." Up until recently, the only way to get this effect was in the studio, but grab an Alesis GuitarFX pedal and check out the amazing Backwards Guitar preset programmed by our own Jim Miller. It uses a special reverse reverb algorithm and a bit of additional tweaking to get that spacey, psychedelic sound. It's worth owning just for this single preset, though it actually has a lot of great sounds. Audio samples can be heard at the Alesis site.