Multiple tracking, which requires an additional 50% of the original fee for solos and duos, is a re-recording over the original track or adding another track, electronically or mechanically, which contains the same material as recorded on the original track. Sweetening, which requires an additional 100% of the original fee for solos and duos, is the addition of a new or variant track over the original track. Group performers are paid an additional 50% of the original fee for unlimited multiple tracking and/or sweetening.