This is music made by four postal workers as they cancel postage! When I listen carefully, I think I can actually hear the spring mechanisms as the stamps hit the ink. I love it as an example of music turning what is normally seen as a boring, repetitive task into something this joyful.
The song was originally recorded in 1975 at the University of Ghana by James Koetting and appeared on a cd accompanying the book Worlds of Music, but you can download the whole clip here. Thanks to Bernie Krause and Anthropologist Steven Feld for helping me track this one down.