Extracting Acapellas using Adobe Audition 1.5

Inverting an instrumental or acapella, and adding it to the original track to extract the respective other works best when both copies are digitally recorded, recordings from master tapes stretch with each use. As long as both of the tracks stay synchronized from beginning to end, and are lined up, the extraction should work. I once tried to extract the acapella from Thriller, by Michael Jackson, only to find out that it wouldn’t work, as the instrumental was a later recording from the master tapes, and wasn’t the exact same tempo, on a very detailed level, to the original.