Rondo (Rondau ) is an orchestral form of the 17th century consisting of repeated "refrain" and different "couplets"(see also :chaconne) . According to Willi Apel it is not for sure whether there is a connection between this form and the medieval Rondo. The rondo form was used mainly by the French harpsichordist (F. Cuperin, Rameau and others) as well as in orchestral and operatic music (Lully).
As Willi Apel indicates, the refrain, as well as each couplet, is a well -
In classical period, possible patterns include: ABA ,ABAGA, ABACADA. The number of couplets (themes) may vary from piece to piece and the recurring elements deviate sometimes ( for example, they may be embellished or shorter).
The Barock forerunner to Rondo was the ritornello. Rondo and ritornello are similar. The difference between them is that in ritornello the main theme returns fragmented and in different keys, while rondo brings back its theme complete and in the same key.
At the end of the 18th century, Rondo evolved in sonata rondo form. In this case, the second theme acts in a similar way to the second theme group in sonata form by appearing for first time in a key other than the tonic and later being repeated in the tonic key. Unlike sonata form, thematic development does not need to occur except possibly in the coda.
As a character type, "Rondo" refers to music that is fast and vivacious-
1.Willi Apel: Harvard dictionary of music, second edition, eighth printing, rondeau.
Carl Philipp Emanuel Bach -