A barbershop quartet is a quartet of singers who sing music in the barbershop genre. It consists of a Lead, the vocal part which generally carries the tune; a bass, the part which provides the bass line to the melody; a tenor, the part which harmonizes above the lead; and a baritone, which sings between the lead and the bass and completes the chord.
Quartets can be male or female, but are generally not mixed. A female barbershop quartet may be referred to as a Sweet Adelines Quartet, and the vocal parts may be referred to as simply lady tenor, lady lead, lady baritone and lady bass, since the roles perform similar functions in the quartet even though the vocal ranges are different.
The tenor generally harmonizes above the lead, making the part the highest in the quartet. So as not to overpower the lead singer, who carries the tune, the part is often sung in falsetto, which is of a softer quality than singing in the modal register, though some quartets do make use of tenors with a softer full voice quality. Notable examples of barbershop quartets which made use of the full-voiced tenor include The Buffalo Bills and Boston Common.
The range of a tenor in barbershop music does not necessarily closely correspond to that of a tenor's range in Classical repertoire, often being more in the range of the classical countertenor range.