How do people upload videos on youtube with copyright music?

I always see videos on youtube with music videos and videos of people with mainstream songs and they play fine. I tried to upload a video for a project with an old Buffalo Springfield "For what its worth" and it muted my whole video and said it was violation of copyright laws or something. Also my video... show more I always see videos on youtube with music videos and videos of people with mainstream songs and they play fine. I tried to upload a video for a project with an old Buffalo Springfield "For what its worth" and it muted my whole video and said it was violation of copyright laws or something. Also my video was all choppy, anyone know about that either? Thanks
11 answers 11