Canon   

In music, a type of counterpoint employing the strictest form of imitation . All the voices of a canon have the same melody, beginning at different times. Successive entrances may be at the same or at different pitches. Another form of canon is the circle canon, or round , e.g., Sumer Is Icumen In . In the 14th and 15th cent. retrograde motion was employed to form what is known as crab canon, or canon cancrizans, wherein the original melody is turned backward to become the second voice. In the 15th and 16th cent. mensuration canons were frequently written, in which the voices sing the same melodic pattern in different, but proportional, note values, i.e., to be sung at different speeds. Bach made noteworthy use of canon, particularly in the Goldberg Variations. Beethoven, Mozart, Haydn, Schumann, and Brahms wrote canons, and Franck used the device in the last movement of his violin sonata. It is an essential device of serial music .