Beatles Rock Band video game. The base release had ~45 or so songs, then later All You Need Is Love song, full Rubber Soul album, full Sgt. Pepper's album and full Abbey Road albums were released as DLC. These "Multi-tracks" were pulled out of the video game files. A lot of these were on youtube, but most of them since have been deleted, in fact, the above posted link to "ABBEY ROAD BUT ITS JUST BASS" youtube video that was made out of exactly those "multi-tracks".
These are still floating around on the internet, just google something like Beatles MOGG.
Speaking of Paul McCartney, there are similar "multi-tracks" of his solo and Wings era stuff as well - for Band on the Run, Hi Hi Hi, Helen Wheels, Jet, Junior's Farm, Let Me Roll It, Maybe I'm Amazed.
