Barbershop Harmony as described by the Barbershop Harmony Society:

• Four-part, unaccompanied, close-harmony singing, with melody in the second voice, called the "lead."
• Tenor (counter-tenor voice) harmonizes above the lead singer; bass sings the lowest harmonizing notes, and the baritone provides in-between notes, to form consonant, pleasing chords.
• Barbershop is a "melting pot" product of African-American musical devices, European hymn-singing culture, and an American tradition of recreational music. It is part of the continuum of American music, sharing roots with gospel and jazz.
• Melodies in the vocal and skill range of the average singer, with lyrical emphasis on simple, heartfelt emotions: love, friendship, mother, moon & June & the girl next door.