A barbershop quartet is a group of four singers who sing music in the barbershop style, characterized by four-part harmony without instrumental accompaniment (a cappella). The four voices are: the lead, the vocal part which typically carries the melody; a bass, the part which provides the bass line to the melody; a tenor, the part which harmonizes above the lead; and a baritone, the part that frequently completes the chord. The baritone normally sings just below the lead singer, sometimes just above as the harmony requires. Barbershop music is typified by close harmony—the upper three voices generally remain within one octave of each other.
While the traditional barbershop quartet included only male singers, contemporary quartets can include any gender combination. All-female barbershop quartets were often called beauty shop quartets, a term that has fallen out of favor. The voice parts for women's and mixed barbershop groups use the same names as those for male groups since the roles perform similar functions in the quartet although the vocal ranges may be different.
