Crab canon

A cancer canon or retrograde canon is a musical palindrome, that is, a canon, which sounds the same backwards as forwards. A voice carries the melody forward, the other voice she wears backwards, in cancer,. When mirror canon or canon inverse, however, is not vertically but horizontally flipped so that the voices of the intervals in opposite directions play ( reverse ). Another form that combines both, is the mirror of cancer or table canon, in which the singers or players sitting opposite each other and have to start in the opposite corners of the same sheet of music. This retrograde - inverse canon is then no axes, but point symmetric to set center.

A well-known cancer canon is found in the Musical Offering by Johann Sebastian Bach.

The motive of cancer canon was later shown by MC Escher playful in graphical form.