Collegiate a cappella, part of a long tradition of unaccompanied singing, is known to date back on American college campuses to at least the colonial era. Considered in the context of college glee clubs, barbershop quartets, early-twentieth-century vocal pop groups, doo-wop groups, and late-twentieth-century a cappella manifestations in pop music, collegiate a cappella is an extension of a very old tradition of close harmony singing---one that includes but also goes beyond the founding of the Yale Whiffenpoofs. Yet despite this important history, collegiate a cappella has until now never been the subject of scholarly examination. In Powerful Voices: The Musical and Social World of Collegiate A Cappella, Joshua S. Duchan offers the first thorough accounting of the music's history and reveals how the critical issues of sociability, gender, performance, and technology affect its music and experience. Just as importantly, Duchan provides a vital contribution to music scholarship more broadly, in several important ways: by expanding the small body of literature on choruses and amateur music; by addressing musical and social processes in a field where the vast majority of scholarship focuses on individuals and their products; and by highlighting a musical context long neglected by musicologists---the college campus. Ultimately, Powerful Voices is a window on a world of amateur music that has begun to expand its reach internationally, carrying this uniquely American musical form to new global audiences, while playing an important role in the social, cultural, and musical education of countless singers over the last century.