A musical form originating in the Baroque period, composed of a principal theme (or “refrain”) alternating with one or more contrasting themes (“episodes”).
It comes from the Ritornello in Italian opera.
The refrain is always in the tonic key, while the episodes are often in another key (sometimes with a bridging section to transition to the new key).
In a sonata rondo, the first ABA section (ABACABA) is the equivalent of the sonata exposition, and the second ABA (ABACABA) functions as the recapitulation, where the second B section is transposed to the tonic key.
Common patterns:
- ABACA: five-part rondo
- ABACABA: seven-part rondo (if it’s ABACAB’A (with the second B transposed to the tonic, then it’s a sonata rondo))
also:
- ABACAB or ABACBA: six-part rondo