I don’t know much about performance rights. That’s a legal issue. It’s true that we ought to follow the laws so long as they are not immoral or lead us into immoral situations. But I kind of doubt that there’s any laws against that…?
Look, in the Catholic faith, we are called to reform our lives. But when something seems fishy to you (like a radical Christian group saying don’t wear makeup, it’s the devil!) that’s probably because it’s not right.
What’s so amazing about Catholicism, is that those things we culturally are aware of as good, actually are good. We don’t demonize proper sex between married people, we don’t demonize makeup, we don’t demonize laughing… or learning lessons from youtube! People who demonize this sort of thing probably shouldn’t be trusted because it’s contrary to what makes sense.
That doesn’t always apply, of course, and there are grey areas… but when something smells fishy, 95% of the time it probably is fishy.
(edit: that being said, as I am not familiar with the law regards to people uploading their music on YouTube, I don’t know if their action is perfectly legit. But I think there is no law preventing you from watching their video and learning)