Free MusicThis is the music we love to find. Music we can use but don't have to pay the composer anything except a good attribution. Too bad this is few and far between.
Royalty-Free MusicThis, on the other hand, is also usually free to download - maybe. Or sometimes there's little beeps over the music or you can only listen to a short snippet of it. But not all the time. For the most part there's a fee attached to the music. But that's okay. These good musicians definitely need supported.
But what you need to watch out is the cost of the music. Most of what you find as Royalty-Free could end up costing you some big bucks. It's a commercial venture. And most vidders are not doing this in the commercial arena. That's when it gets hard deciding if you really want to spend $100 on that royalty-free disk just to get that one song.
If you have the available cash then go for it. I, on the other hand, will have to pass and continue looking for music I can afford.