Barbershop harmony is a style of vocal music characterized by four-part harmony, with the melody sung in the top voice. It is typically performed a cappella, with the CHORD being sung by the other three voices. The term 'barbershop harmony' comes from the fact that the style was popularized in the late 19th century by African American barbershops. The style has since become popular worldwide, and is now associated with a wide range of musical genres.