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 Society (BHS), "Barbershop music features songs with understandable lyrics and easily singable melodies, whose tones clearly define a tonal center and imply major and minor chords and barbershop (dominant and secondary dominant) seventh chords that resolve primarily around the circle of fifths, while making frequent use of other resolutions." Slower barbershop songs, especially ballads, often eschew a continuous beat, and notes are often held (or sped up) ad libitum. Except for the bass, the voice parts in barbershop singing do not correspond closely to their classical music counterparts; the tenor range and tessitura are similar to those of the classical