Carlos Gardel/Francisco Canaro

Carlos Gardel was tango's first superstar and still one of its most enduring performers. Revered as an icon in Argentina ever since his tragic death in 1935, Gardel -- nicknamed "El Zorzal Criollo" ("The Creole Thrush") -- was the first singer to adopt the tango as a form of popular song. Previously, it had been entirely instrumental dance music, looked down upon by the cultural elite for its common origins and earthy sensuality. Gardel didn't change those qualities, but his advocacy certainly popularized the genre beyond all expectations. Thanks to extensive touring and a bud...