No offence, but that's a weird obsession with bootlegs, if you don't even know what it is. There is no reason to do a bootleg, if you can do it legally. If the labels/artists/whatevs sees reason, you will get trouble, and might have to pay . The only reason people aren't getting trouble for it, is because it goes unnoticed, be it because you only share it with a few friends or on sites like soundcloud. Altering somebody's music is genereally not allowed, unless written in the licence. Some music is under a "free" licence or whatever it is called, might be worth checking out - but then it's not really a bootleg. I can't remember which site, but there was one with a lot of that kind of music. Freesound.org also has a few, I think. Or, as mentioned, you can clear the samples by asking for permission.
