Barbershop harmony is a style of vocal music characterized by consonant four-part chords for every melody note, except for occasional short passages which may be sung by less than four voices. It is invariably sung without accompaniment and is described as “A Cappella” music.

The parts, or voices, from highest to lowest, are called Tenor, Lead, Baritone and Bass. The melody is usually carried by the Lead, with Toner consistently singing higher harmonizing notes, the Bass singing the lower harmonizing notes, and the Baritone completing the chord, either above or below the Lead. The melody may occasionally be sung by the Baritone or Bass, but not by the Tenor except for an infrequent note or two to avoid awkward voicing of a chord, or for special effects, such as in introductions or in the coda (“tag” or song ending).

Barbershop music uses a minimum of sixth and ninth chords, and dissonant chords containing the Major 7th or Minor 2nd intervals. It features triads and Major-Minor 7th chords (“Barbershop seventh chords”) resolving primarily on the circle of fifths. The basic harmonization may be embellished with additional chord progressions wherever these may artistically serve to maintain rhythmic interest, to carry over between phrases, and to introduce or close the song effectively.

Barbershop music is not sung in the tempered tuning of mechanical keyboard instruments, but in more acoustically correct tuning in which the singers pay close attention to enharmonic pitch adjustments, thus producing a clear interlocking of the voices and a reinforcement of the overtones which gives the characteristic “ring” of the chords.