Escamillo has mentioned two great South American composers who use folk themes; unfortunately they are no longer living.
The violinist Gidon Kremer and a group of musicians including Horacio Ferrer released Piazzolla's masterpiece "Maria de Buenos Aires," a tango operita, on 2cds in 1998 with the complete libretto. A set of discs issued by Milan -BMG covers many of his performances with his Quinteto. I play them frequently.

Recently, I Musici de Montreal recorded Ginastera's Concerto for Strings on the Chandos label. His Estancia Suite, based in part on folk melodies, is, or should be, well-known.