Sosa was born in Las Piedras, a Canelones Department suburb of Montevideo, Uruguay.

Working with numerous other orchestras, he was reunited with Pontier in 1955, with whom he recorded several best-selling albums on the RCA Victor and Columbia labels and became one of the most important tango singers in the genre's history.

Sosa also published a book of poetry, Dos horas antes del alba ("Two Hours Before the Dawn"), in 1960.

Following his switch to Columbia Records in 1961, the Pontier orchestra incorporated a new bandoneonist, Leopoldo Federico, and the association helped make the group the most successful in its genre, at the time.

He was behind the wheel of an Auto Union 1000S Fissore coupé when, in the early hours of November 26, 1964, he crashed at high speed into a traffic light on Buenos Aires' Figueroa Alcorta Avenue, killing himself at age 38.