Full song backing tracks provide a fuller arrangement of a song than song rhythm tracks do but they may be limited in the facilities to re-arrange / re-mix the backing track. For instance, there might be instruments included that the musicians wish to remove from the mix. Song Rhythm Tracks can be used as the basis for an arrangement generally without requirements of re-arranging the song rhythm tracks. Full song backing tracks are often used by singers as their sole accompaniment. Song rhythm tracks are used by single, or groups of, musicians that do not have a drummer.