Back in Buenos Aires later that year he put together the first, and perhaps most famous, of his quintets, the first Quinteto, initially comprising bandoneon (Piazzolla), piano (Jaime Gosis), violin (Simón Bajour), electric guitar (Horacio Malvicino ) and double bass (Kicho Díaz). Of the many ensembles that Piazzolla set up during his career it was the quintet formation which best expressed his approach to tango.Piazzolla & his orchestra at television network Canal13 in 1963. (AGN)
In 1963 he set up his Nuevo Octeto and the same year premiered his Tres Tangos Sinfónicos, under the direction of Paul Klecky, for which he was awarded the Hirsch Prize.
In 1965 he released El Tango, an album for which he collaborated with the Argentine writer Jorge Luis Borges. The recording featured his Quinteto together with an orchestra, the singer Edmundo Rivero and Luis Medina Castro reciting texts.
In 1966 he left Dedé Wolff and the following year signed a five-year contract with the poet Horacio Ferrer with whom he composed the operetta María de Buenos Aires, with lyrics by Ferrer. The work was premiered in May 1968 with the singer Amelita Baltar in the title role and introduced a new style of tango, Tango Canción (in English: Tango Song). Soon after this he began a relationship with Amelita Baltar. The following year he wrote Balada para un loco with lyrics by Ferrer which was premiered at the First Iberoamerican Music Festival with Amelita Baltar and Piazzolla himself conducting the orchestra. Piazzolla was awarded second prize and the composition would prove to be his first popular success.
In 1970 Piazzolla returned to Paris where with Ferrer he wrote the oratorio El pueblo joven later premiered in Saarbrücken, Germany in 1971. On May 19, 1970 he gave a concert with his Quinteto at the Teatro Regina in Buenos Aires in which he premiered his composition Cuatro Estaciones Porteñas.
Back in Buenos Aires he founded his Conjunto 9 (a.k.a. Nonet), a chamber music formation, which was a realisation of a dream for Piazzolla and for which he composed some of his most sophisticated music. He now put aside his first Quinteto and made several recordings with his new ensemble in Italy. Within a year the Conjunto 9 had run into financial problems and was dissolved and in 1972 he participated in his first concert at the Teatro Colón in Buenos Aires, sharing the bill with other Tango orchestras.