After spending two years abroad, first in Cuba and later in Paris, he returned to Argentina, and in 1969 he joined the new Osvaldo Pugliese orchestra, which was formed following a decision by its former players, who wanted to play only with the ensemble, Sexteto Tango, that they had recently put together.
In 1976 Mederos started a new group, Generación Cero, which attracted a cult following, trying to create a fusion between jazz, rock and the music of Buenos Aires.
In 2000 he released the record Tango Mederos-Brizuela, with another disc that included the soundtrack of the film Las veredas de Saturno that he had composed twenty years before.
In 1999 Mederos formed a quintet with the pianist Hernán Posetti, the violinist Damián Bolotín, the guitarist Armando de la Vega and the double-bassist Sergio Rivas, who together recorded Eterno Buenos Aires.
Mederos composed the soundtrack and was also the lead actor in the French-Argentine film Les Trottoirs de Saturne (1986), directed by Hugo Santiago.