Mountain music, old-timey music, American roots music—whatever it is called, the folk music that evolved within the unique geographic, economic and cultural terrain of the Appalachian South would later develop into the commercial forms of bluegrass, country and western, and rock and roll. A backstage look at the musicians featured on the soundtrack to the Coen Brothers film, O Brother, Where Art Thou?, this features live performances by Alison Krauss, Emmylou Harris, Gillian Welch, and others.