This video of Canon 1 à 2 from J. S. Bach's Musical Offering (1747) being turned into a Moebius strip, then played in two directions at the same time would have been good to watch and listen to while I was reading the mind-bending Gödel, Escher, Bach: An Eternal Golden Braid many years ago. (via cgr 2.0)
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. Come and hear Mark speak at the ALA conference in Chicago on July 1.