Barbershop harmony is a style of unaccompanied vocal music characterised by consonant four-part chords for every melody note in a predominantly homophonic texture. The melody is consistently sung by the lead, with the tenor harmonising above the melody, the bass singing the lowest harmonising notes, and the baritone completing the chord.

British Association of Barbershop Singers

How did it all begin?

Barbershop quartets often are characterized as four dandies, perhaps bedecked with straw hats, striped vests and handlebar mustaches. These caricatures of the barbershop tradition are not only a quaint symbol of small-town Americana, but have some historical foundation. Barbershop music was indeed borne out of informal gatherings of amateur singers in such unpretentious settings as the local barber shop. However....

....the earliest known references to the term "barbershop," as it refers to a particular chord or brand of harmony, link it with African-American society. As early as 1900, an African-American commentator with the self-imposed moniker "Tom the Tattler" accuses barbershop quartet singers of "stunting the growth of `legitimate,' musically literate black quartets in vaudeville." The 1910 song "Play That Barber Shop Chord," which before Abbott's discovery of the Tattler's commentary was considered the earliest reference to the term "barbershop," also associates the genre with African-American society.

Barbershop Harmony Society