The musical term a capella “ah-kuh-pel-uh” means “without accompaniment.” In some churches, the choir sings without an organ or other instrumental accompaniment, i.e, they sing a capella. An a capella performance is entirely vocal.
College glee clubs (choral groups) and barbershop quartets sing a capella.
The Anonymous Four is a well-known singing group of four women who sing without instrumental accompaniment.
You can hear an example of a capella singing at the site of another women’s a capella group: AKSARA