This document discusses voice classification and vocal ensembles. It describes the main categories of human voices as female (including children's voices) and male. Female voices are classified as soprano, mezzo soprano, contralto, and treble. Male voices are classified as tenor, baritone, and bass. Vocal ensembles can be classified by number of voices, voice types, or musical style. Examples of ensembles include choirs, which can be for children, men, women, or mixed groups, as well as duets, trios, and larger groups.