Rondellus

In music rondellus is the formalized interchange of parts or voices according to a scheme, often used in English conducti and frequently in English motets of the late thirteenth and early fourteenth centuries, but never used for an entire piece. For example:

A B C D E F C A B  F D E B C A  E F D

where the italicized letters represent music with text and the other letters are melismatic.