Barbershop Harmony is a style of a capella, four part, close harmony, vocal music.
A capella means that it is unaccompanied. The word comes from the Latin meaning “in the chapel style” from an era when musical instruments were considered to be the work of the devil and were banned in church services. It doesn’t mean that we sing church music, only that it is not accompanied.
Four part means that the smallest group that can sing barbershop is four voices, a quartet. In a chorus, there are still only four different voice parts, there is just more than one person singing each part. The parts are called lead (singing the melody), bass (singing the low notes), tenor (singing a high harmony part over the melody) and baritone (singing the notes that nobody else wants!).
It is close harmony because it is always sung by single voice groups, either all male or all female and that, of course, limits the range of notes that can be sung. The interval between the highest and lowest notes are always less that two octaves and, frequently, much less.
It is arranged in such a way that the different voice parts blend together in support of each other. This makes it possible for people with untrained voices to produce exciting and creative music.
For more information on the history of the style and its technicalities, visit the Barbershop Harmony Society site. This Society was formed in 1938, in the USA, by a few men who felt that the barbershop style was vanishing as a result of trends in entertainment, including radio, and they determined that it was worth some effort to preserve it.