We do underwater video from dive trips. We started using just music from our CD collection until my honey put a snippet from one on you tube and got told to take it down for copywrite infringement. Then he found a site that has original music out there you could use for free as long as you acknowledged the artist, which he did and again an artist tried to get him to pay for it but he had proof he took it from the site under their rules. From what I understand you can now use popular music as long as you allow them to advertise. I'm assuming if you are just keeping it for your own use and not putting it anywhere public you could use whatever you wanted. We always watch our raw footage and edit it down a little for time then try to find a song that fits the action.