Well, you wouldn't be uploading song remixes to Freesound in the first place, would you? (Although I've heard some weird stuff in there.

) The history of tracker music is full of copyright breaches but generally it doesn't interest commercial music copyright holders mainly because the songs don't generate profit and we're fairly underground (=unknown). It is when you go commercial with your music, even "big shots" like Purple Motion play it safe and replace the original samples ("Get down!", "Ten seconds to transmission"...) with re-recordings.