A round or perpetual canon is a musical composition, a limited type of canon, in which a minimum of three voices sing exactly the same melody at the unison (and may continue repeating it indefinitely), but with each voice beginning at different times so that different parts of the melody coincide in the different voices, but nevertheless fit harmoniously together (Johnson 2001). It is one of the easiest forms of part singing, as only one line of melody need be learned by all parts, and is part of a popular musical tradition. They were particularly favoured in glee clubs, which combined amateur singing with regular drinking (Aldrich 1989, introductory essay, 8–22, especially at 21: "Catch-singing is unthinkable without a supply of liquor to hand..."). The earliest known rounds date from the 12th century.
Though not all rounds are nursery rhymes, "Row, Row, Row Your Boat" is a well-known children's round for four voices. Other well-known examples are "Frère Jacques" and "Three Blind Mice" (Hoffman 1997, 40).
A catch is a round in which a phrase that is not apparent in a single line of lyrics emerges when the lyrics are split between the different voices. "Perpetual canon" refers to the end of the melody leading back to the beginning, allowing easy and immediate repetition. Often, "the final cadence is the same as the first measure" (Walton 1974, 141).
The term "round" first appears in English in the early 16th century, though the form was found much earlier. In medieval England, they were called rota or rondellus. Later, an alternative term was "roundel" (e.g., David Melvill's manuscript Ane Buik off Roundells, Aberdeen, 1612). Special types of rounds are the "catch" (a comic English form found from about 1580 to 1800), and a specialized use of the word "canon", in 17th- and 18th-century England designating rounds with religious texts (Johnson 2001). The oldest surviving round in English is "Sumer Is Icumen In" (Hoffman 1997, 40) Play (help·info), which is for four voices, plus two bass voices singing a ground (that is, a never-changing repeating part), also in canon. However, the earliest known rounds are two works with Latin texts found in the eleventh fascicle of the Notre Dame manuscript Pluteo 29.1. They are Leto leta concio (a two-voice round) and O quanto consilio (a four-voice round). The former dates from before 1180 and may be of German origin (Falck 1972, 43–45, 57). The first published rounds in English were printed by Thomas Ravenscroft in 1609... "Three Blind Mice" Play (help·info) appears in this collection, although in a somewhat different form from today's children's round:
- Three Blinde Mice,
- three Blinde Mice,
- Dame Iulian,
- Dame Iulian,
- The Miller and his merry olde Wife,
- shee scrapte her tripe licke thou the knife.
The canon, or rule, of a simple round is that each voice enters after a set interval of time, at the same pitch, using the same notes. (Mead 2007, 371)
What makes a round work is that after the work is divided into equal-sized blocks of a few measures each, corresponding notes in each block either are the same, or are different notes in the same chord. This is easiest with one chord, as in "Row, Row, Row Your Boat" Play (help·info):
A new part can join the singing by starting at the beginning whenever another part reaches any asterisk in the above music. If one ignores the sixteenth notes that pass between the main chords, every single note is in the tonic triad—in this case, a C, E, or G.
The texture is simpler, but it uses a few more notes; this can perhaps be more easily seen if all four parts are run together into the same two measures:
Serious composers who turned their hand to the round format include Thomas Arne, John Blow, William Byrd, Henry Purcell, Louis Hardin, Joseph Haydn, Wolfgang Amadeus Mozart, Ludwig van Beethoven, and Benjamin Britten (for example, "Old Joe Has Gone Fishing", sung by the villagers in the pub to keep the peace, at the end of act 1 of Peter Grimes) (Howard 1969, 15). Examples by J. S. Bach include the regular canons, Var. 3 and Var. 24 of the Goldberg Variations, and the perpetual canons, Canon 7 of The Musical Offering and Canon a 2 Perpetuus (BWV 1075) (Smith 1996). Several rounds are included amongst Arnold Schoenberg's thirty-plus canons, which "within their natural limitations ... are brilliant pieces, containing too much of the composer's characteristically unexpected blend of seriousness, humour, vigour and tenderness to remain unperformed" (Neighbour 1964, 681).
- Aldrich, Henry. 1989. The Aldrich Book of Catches, edited by B. W. Robinson and R. F. Hall. London: Novello.
- Falck, Robert. 1972. "Rondellus, Canon, and Related Types before 1300". Journal of the American Musicological Society 25, no. 1 (Spring): 38-57.
- Hoffman, Miles. 1997. The NPR Classical Music Companion: Terms and Concepts from A to Z. Boston: Houghton Mifflin. ISBN 9780618619450. Reprinted as The NPR Classical Music Companion: An Essential Guide for Enlightened Listening, Paw Prints binding, 2005. ISBN 9781435294042.
- Howard, Patricia. 1969. The Operas of Benjamin Britten; An Introduction. New York and Washington: Frederick A. Praeger, Publishers.
- Johnson, David. 2001. "Round". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers. ISBN 9781561592395; ISBN 9780333608005
- MacDonald, Margaret Read, and Winifred Jaeger (2006). The Round Book: Rounds Kids Love to Sing. Little Rock: August House. ISBN 9780874837865.
- Mead, Sarah. 2007. "Renaissance Theory". In A Performer's Guide to Renaissance Music, second edition, revised and expanded, edited by Jeffery T. Kite-Powell, 343–73. Publications of the Early Music Institute. Bloomington: Indiana University Press. ISBN 978-0-253-34866-1.
- Neighbour, Oliver W. 1964. "Schoenberg's Canon's". The Musical Times 105, no. 1459 (September): 680–81.
- Norden, Hugo (1970). The Technique of Canon. Branden Books. ISBN 9780828318396.
- "Anatomy of a Canon", The Canons and Fugues of J. S. Bach.
- Walton, Charles W. 1974. Basic Forms in Music. New York: Alfred Publishing Co. ISBN 9780882840109; ISBN 9780882840253.