How does Aucassin and Nicolette alternate between verse and prose?

Aucassin et Nicolette is a 13th-century French chantefable, a unique literary form characterized by its structure of alternating sections of verse and prose.12

In this format, the verse sections were intended to be sung, while the prose sections were meant to be recited. The term itself, derived from the Old French cantefable (literally "it sings and it narrates"), highlights this dual mode of performance.12

While the work is the only surviving example of this specific genre, the author utilized the two modes differently: the verse sections are noted for their vigor and musicality, whereas the prose sections serve as the narrative framework for the story of the lovers Aucassin and Nicolette.1