form of popular choral music consisting of unaccompanied male singing, with three voices harmonizing to the melody of a fourth voice. The voice parts are tenor, lead, baritone, and bass, with the lead normally singing the melody and the tenor harmonizing above. The emphasis is on close, carefully arranged harmony, synchronization of word sounds, and the use of such devices as variation of tempo, volume level, diction, colour, and phrasing. Phrases are often repeated for echo effect, and musical arrangements usually employ syncopated ragtime and other nostalgic song styles.

Although barbershop quartet singing is associated with the United States, its origins (in the 19th century) are obscure: it may date from an era when American barbershops formed social and musical centres for a neighbourhood's males, or it may refer back to the British expression “barber's music,” denoting an extemporized performance by patrons waiting to be shaved and referring to a barber's traditional role as a musician. In any event, the modern Society for the Preservation and Encouragement of Barber Shop Quartet Singing in America (SPEBSQSA, Inc.) was founded by Owen Clifton Cash, Rupert I. Hall, and 24 other men who attended a first meeting and songfest at the Tulsa Club in Tulsa, Okla., U.S., on April 11, 1938. The society flourished, and by the late 20th century it had more than 800 chapters with more than 38,000 members. It holds an annual convention and contests, in which about 50 quartets and 16 choruses compete, and it publishes the bimonthly magazine The Harmonizer. International headquarters are in Kenosha, Wis.