Pink Floyd!

If the song “Empty Spaces” from legendary British psychedelic rock band Pink Floyd (from the album “The Wall”) is played backwards, the phrase “Congratulations, you have discovered the secret message.

Send your answer to Old Pink, care of the funny farm, Chalfont…” can be heard. The message is interrupted by a voice saying “Roger, Carolyn's on the phone.” Carolyn Christie was the band's bassist's Roger Water's wife.