These practice tracks are specially remixed versions of the full-choir audio demos. Each practice track features a primary vocal part while the volume levels of the surrounding vocal parts are significantly reduced to allow the featured vocal part to be heard very clearly.
Each pack contains the part-dominant tracks for all of the vocal parts in that particular arrangement. So if you choose the SAB pack, you will receive the Soprano, Alto, and Baritone practice tracks to privately share with members of your choir.