A barbershop group is a type of vocal ensemble consisting of four or more singers. The most common type is the four-part harmony group, also known as a QUARTET. Barbershop groups typically sing a cappella, meaning without instrumental accompaniment, and often perform in a style that is characterized by close harmonies and a lighthearted, humorous approach. Barbershop singing has been popular since the late 19th century and continues to be enjoyed by audiences around the world.