Ads would be a knee jerk reaction. Try to find out how users are using it, what they're using it for (e.g. household playlist or live performances?) and what features they would pay for, then offer a pro version.
I could see this being a great tool for VJ mashups, especially at 720p.
I think this is a very good point. You may find that there is more to be made selling songs/albums/playlists via affiliate channels, or like stated, offering pro features. DJ's may even be using it to trial new vinyls before they buy. If nothing else understanding the use should allow you to better tailor the site to drive up traffic if you do decide to roll out ads.
I could see this being a great tool for VJ mashups, especially at 720p.