You're probably an artist looking for instructions on how to get your music taken down from those sites. Wouldn't it be nice if it were opt-out? Alas, it is not. You have to find every violation and report it. It's a game of whack-a-mole, many of the files pop up again within days.
Youtube uses this option. If a copyright owners "opt out," Youtube automatically block the video the very second it is uploaded.