An anonymous reader writes "Complaints about copyright infringement on YouTube keep Google busy. If you have any doubts, just look at the Viacom copyright suit. But the problems aren't just about uploaded videos, but sometimes the music accompanying the videos. A patent application shows that Google has worked on a system to automatically identify infringing music by comparing a digital signature of a soundtrack to signatures of existing music. Users who upload videos could opt to completely remove the video, swap the soundtrack for something approved, or to mute the video. Of course, there doesn't seem to be a provision if you're using existing music with permission."