R. Herges: DOI; 10.1021/cr0505425
"A canon which is probably one of the oldest man-made
examples of an object with Möbius topology. The canon
cancricans (crab canon) is written for two violins playing
the same score in two different directions. If you cut the
score, paste it in such way that it forms a band with the
notes of the first violin on top and those of the second
violin below, fold it lengthwise between the two notes,
give one end a half twist and join both ends, you end up
with a endless Möbius shaped score. After every turn the
two violins change their parts."
