Barbershop harmony is generally considered to be one of the few uniquely American-born musical styles, alongside jazz, with which it shares origins. The simplest definition of barbershop centers around:
relatively simple melodies,
sung in four-part harmony,
without instruments (a cappella),
with the melody carried in the lead part, a tenor harmonizing above that, a bass singing fundamental harmonies, and a baritone filling in above and below the melody.