Barbershop, an original American art form, is four-part vocal music sung without any instrumental accompaniment. The four voice parts are Lead (the melody), Tenor ( above the melody), Baritone (about the same range as the lead, but a harmony part), and Bass ( below the melody).  What makes barbershop unique is that it is "close harmony", meaning that the notes sung by the four parts, unlike traditional choral music, are placed very close together.