Not sure if anyone else has been following Stems files, but for those with a DJ interest should defintely have been keeping up to date. Beatport Pro now sells stem file variants of tracks and the below video sets out what you can do with an appropriate mixer/controller.
Stems files provide that the track you are playing is split into 4 underlying tracks: eg drums, bass, synth/effect, vox. You can then layer effects onto an individual underlying sub-track, control the volume of that sub-track, loop etc etc. Absolutely brilliant fun!
If you want to jump direct to an example, go to 7 mins int he video and listen from there. Makes me want to unload the wallet on an S8, awesome stuff!