Barbershop music encompass both men's and women's singing in the barbershop style – in quartets and choruses. Sweet Adelines International and Harmony, Inc. are two women's barbershop singing organizations that operate globally and in North America, respectively. Other women's organizations include the Ladies Association of Barbershop Singers (LABBS) in the United Kingdom, the Spanish Association of Barbershop Singers (SABS) in Spain, and the Irish Association of Barbershop Singers (IABS) in Ireland. A barbershop quartet is an ensemble of four people who sing a cappella in the exacting barbershop music genre. In North America most male barbershop quartet singers belong to the Barbershop
Barbershop music recording industry their performances were recorded and sold. Early standards included songs such as "Shine On, Harvest Moon", "Hello, Ma Baby", and "Sweet Adeline". Johnson noted in the 1920s how the genre had already crossed racial barriers. Barbershop music was very popular between 1900 and 1919, and some of the most popular quartets were the Haydn Quartet, the American Quartet, and the Peerless Quartet. Modern barbershop quartets often costume themselves in gaudy versions of the vaudeville dress of this time, with boaters and vertically striped vests. Composer and pianist Scott Joplin incorporated a barbershop quartet into his 1911 opera "Treemonisha".