A crab canon—also known by the Latin form of the name, canon cancrizans—is an arrangement of two musical lines that are complementary and backward, similar to a palindrome. Originally it is a musical term for a kind of canon in which one line is reversed in time from the other (e.g. FABACEAE <=> EAECABAF). A famous example is found in J. S. Bach’s The Musical Offering, which also contains a canon (“Quaerendo invenietis”) combining retrogression with inversion, i.e., the music is turned upside down by one player – also known as a table canon.

What is remarkable about this is that Bach makes something so intricately complex sound so sublime.