In American music, the notion of "roots" has been a powerful refrain, but just what constitutes our true musical traditions has often been a matter of debate. As Benjamin Filene reveals, a number of competing visions of America's musical past have vied for influence over the public imagination in this century.

Filene builds his story around a fascinating group of characters--folklorists, record company executives, producers, radio programmers, and publicists--who acted as middlemen between folk and popular culture. These cultural brokers "discovered" folk musicians, recorded them,...