Despite the prevalence of the quintet formation and the ABABC compositional structure, Piazzolla consistently experimented with other musical forms and instrumental combinations. In 1965 an album was released containing collaborations between Piazzolla and Jorge Luis Borges where Borges's poetry was narrated over very avant-garde music by Piazzolla including the use of dodecaphonic (twelve-tone) rows, free non-melodic improvisation on all instruments, and modal harmonies and scales. In 1968 Piazzolla wrote and produced an "operita", "María de Buenos Aires", that employed a larger ensemble including flute, percussion, multiple strings and three vocalists, and juxtaposed movements in Piazzolla's own style with several pastiche numbers ranging from waltz and hurdy-gurdy to a piano/narrator bar-room "scena" straight out of "Casablanca".