During this period he began to study classical orchestration with Alberto Ginastera, the eminent Argentine composer, and took piano lessons with the Argentine classical pianist Raúl Spivak.
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His works would quickly became classics in the repertoire of some of the most popular tango orchestras of the day, including those of Anibal Troilo, Osvaldo Fresedo and Jose Basso.
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He concentrated now on the study of classical music, including a year in Paris with the French classical composition teacher Nadia Boulanger, before returning to Buenos Aires where he would finally commit himself to tango with the founding of his next ensemble, Octeto Buenos Aires, in 1955.
The following year he joined Astor Piazzolla’s Octeto Buenos Aires with the bandoneons of Piazzolla and Roberto Pansera (later replaced by Leopoldo Federico), the violin of Hugo Baralis, the cello of José Bragato, the double bass of Aldo Nicolini (later replaced by Juan Vasallo), the electric guitar of Horacio Malvicino and the piano of Atilio Stampone.
Upon hearing a recording of Ferrer reciting these poems, accompanied by the guitarist Agustín Carlevaro, Piazzolla invited him to collaborate on the writing of the opereta María de Buenos Aires.
In 1968 Piazzolla put together an orchestra, including Díaz, to perform his operetta María de Buenos Aires, and between 1971 and 1972 Díaz played with Piazzolla’s Conjunto 9.
The ensemble's objective is to approach the tango repertoire ranging from its earliest manifestations ("guardia vieja") to contemporary pieces, such as those of Piazzolla, Blázquez, Pujol, etc.