This document summarizes the classification of human voices and vocal ensembles. It describes that there are two main groups of voices - female and male - which are classified by their timbre and range. It then lists the different voice types from highest to lowest for female voices as soprano, mezzo soprano, and contralto and for male voices as tenor, baritone, and bass. The document concludes by explaining that vocal ensembles can be classified by their number of voices, types of voices, or style of music performed.