A crab canon (also known by the Latin form of the name, ''canon cancrizans''; as well as ''retrograde canon'', ''canon per recte et retro'' or ''canon per rectus et inversus'')
[Kennedy, Michael (ed.). 1994. "Canon". The Oxford Dictionary of Music, associate editor, Joyce Bourne. Oxford and New York: Oxford University Press. .] is an arrangement of two musical lines that are complementary and backward. If the two lines were placed next to each other (as opposed to stacked), the lines would form something conceptually similar to a
palindrome
A palindrome is a word, number, phrase, or other sequence of symbols that reads the same backwards as forwards, such as the words ''madam'' or ''racecar'', the date and time ''11/11/11 11:11,'' and the sentence: "A man, a plan, a canal – Panam ...
. The name 'crab' refers to the fact that crabs are known to walk backward (although they can also walk forward and sideways). It originally referred to a kind of
canon
Canon or Canons may refer to:
Arts and entertainment
* Canon (fiction), the conceptual material accepted as official in a fictional universe by its fan base
* Literary canon, an accepted body of works considered as high culture
** Western can ...
in which one line is played backward (e.g. FABACEAE played simultaneously with EAECABAF). An example is found in
J. S. Bach's ''
The Musical Offering
''The Musical Offering'' (German: or ), BWV 1079, is a collection of keyboard canons and fugues and other pieces of music by Johann Sebastian Bach, all based on a single musical theme given to him by Frederick the Great (King Frederick II of Pr ...
'', which also contains a
table canon
A Table canon is a retrograde and inverse canon meant to be placed on a table in between two musicians, who both read the same line of music in opposite directions. As both parts are included in each single line, a second line is not needed. Bac ...
("Quaerendo invenietis"), which combines