Art Rosenbaum is a folk revivalist of the old school. He believes that traditional ballads, blues, spirituals, and fiddle tunes are among the glories of American culture. Last fall, Dust-to-Digital released Art of Field Recording: Volume I, a four-CD retrospective of Rosenbaum’s work. It contained everything from ring shouts and murder ballads to a song about twenty frogs going to school. It was full of throaty voices and clanging banjos and the incidental music of daily life—babies crying, bar glasses clinking, cicadas on a summer night.