Hell, it might all be illegal, but ask yourself why. It's because it is the easiest way of protecting rights and giving the owners of those rights the ability to enforce them if need be. The law is all-encompassing, simply because it'd have to have hundreds and hundreds of pages if it wasn't - and then it could be subject to a lot more interpretation. Original artists are generally not gonna give a crap if you play a midi of one of their songs, or download a guitar tab, or record a song off the radio, or watch a youtube video with their unlicensed music in it. The greedy corporations such as the RIAA are the only ones actively cracking down on such things, and they have already proven to be unsound of mind, suing a russian company for trillions of dollars - when really it's all scare tactics. Illegal? Of course. Unethical? I guess that's the question that needs to be asked of yourself. If you're intending to sell your game, I would say it most definitely is. Otherwise you need to think about it.