rondo

A musical structure in which restatements of the initial theme are separated by contrasting episodes, eg on the pattern A–B–A–C–A–B–A, perhaps with an introduction and a coda. In the sonata rondo, the ‘B’ theme of this scheme is stated first in a related key, returning in the home key, and the ‘C’ theme may be replaced by development.

Rondo, and its French equivalent rondeau, is a word that has been used in music in a number of ways, most often in reference to a musical form, but also in reference to a character-type that is distinct from the form. Although now called rondo form, the form started off in the baroque period as the ritornello form, coming from the latin word ritornare meaning "to return", indicating the return to the original theme or motif ("A"). Rondo and Ritornello Forms in Tonal Music

In rondo form, a principal theme (sometimes called the "refrain") alternates with one or more contrasting themes, generally called "episodes," but also occasionally referred to as "digressions," "couplets," or "subordinate themes."

The form began to be commonly used from the classical music era, though it can be found in earlier works.

Rondo was often used by baroque composers to write Ritornello rondos. They were used in the fast movements of baroque concertos and contrast the whole orchestra (who play the main theme) against soloists (who play the episodes.) But Ritornello does differ slightly from other Rondos in that the theme is often different when it recurs but is always distinguishable as the same theme.

A common expansion of rondo form is to combine it with sonata form, to create the sonata rondo form. Here, the second theme acts in a similar way to the second theme group in sonata form by appearing first in a key other than the tonic and later being repeated in the tonic key.

Rondo as a character-type (as distinct from the form) equates to music that is fast and vivacious—normally allegro.