Tracked out audio files, also called stems, are sub mixes of an instrumental. For example, an instrumental might have the four stems: Bass, Beat, Percussion, and Instruments. The Bass stem being the bass; the Beat stem being the kick and the snare; The Percussion stem being the hi-hats, shakers, and crash cymbals; and the Instruments stem being the strings, organs, and synths. All of these stems are the full duration of the instrumental and can be layered together to recreate the stereo mix of the original instrumental. The reason for stems is that they allow for more precise fine tuning while mixing a song. For example, one can adjust the gain on the Bass without affecting the low end of the Cellos. Or one can mold the cymbals around the vocals without affecting the punch of the snare. Although TOFSOUND beats come already professionally mixed, depending on the particular artist's vocals or the sound of the rest of their album, adjustments may want to be made in mastering. With stems these adjustments can be made much more accurately and easily.