In the enigmatic Canon 1 a 2 from J. S. Bachs Musical Offering (1747) (also known as crab canon or canon cancrizans), the manuscript shows a single score, whose beginning joins with the end. This space is topologically equivalent to a bundle of the line segment over the circle, known as a Möbius strip. The simultaneous performance of the deeply related forward and backward paths gives appearance to two voices, whose symmetry determines a reversible evolution. A musical universe is built and then is unplayed back into silence.1