Barbershop quartets, a type of music group fashionable in early twentieth-century America, had a dramatic influence on American popular music styles. The sweet, close harmony of the quartets, the arrangement of voice parts, and their improvisational...

Barbershop harmony, as codified during the barbershop revival era (1940s-present), is a style of a cappella, or unaccompanied vocal music characterized by consonant four-part chords for every melody note in a predominantly homophonic texture. Each of...