Canon

Canon (Greek kanon, “standard”), musical composition in which one voice or part introduces a melody (the “subject”) and, after a given number of beats, a second voice repeats or answers the melody note for note, either on the same pitch or at a higher or lower pitch. A third voice may enter, or begin the melody, at the given number of beats after the start of the second voice, and so on. If the imitation is at a different pitch, the subject may be altered slightly to fit the tonality of the composition. If the subject melody leads back into its own beginning so that the piece can be repeated endlessly, the canon is termed circular. The most common kind of circular canon is called a round.

More complicated ways of writing the answer in a canon include augmentation and diminution (lengthening or shortening the notes of the answering voice); inversion (turning the subject upside down by making each rising interval a falling one and vice versa); retrogression (sometimes called crab canon or cancrizans) giving the subject notes in reverse order; writing the answer in both inversion and retrogression; and repeating the melody pitches of the subject but changing its metre and note durations (mensuration canons). Canonic imitation is often employed for several bars in contrapuntal compositions. A well-known work featuring canons is the Goldberg Variations by J. S. Bach, a set of 30 variations on a theme in which every third variation is a canon, at ever-expanding intervals—the first is at the unison, the second has the answer a major second above the subject, the third has the answer a third higher, and so on up to a ninth. Although the high point of canon as a compositional technique was in the late 15th century, it has become increasingly interesting to 20th-century composers such as Anton Webern and Carl Ruggles, who were often inspired by early-Renaissance models. The earliest known piece that is a canon from start to finish is the 13th-century anonymous English composition “Sumer is Icumen In”.