Quote: "Except its probably not the artists who say no, its their labels."
Thats what happened with "Pitiful" Al had the artists permission but the label said no. Though Al could have released the song anyway without permission he decided to make it a free song for download to keep his label from pissing off the other.
Quote: "its the same for cover bands, there is no problem creating your own version of a song as long as you dont sample any exact pieces of music its fine. copyright free."
Untrue, Al gets away with it under a certain set of parody laws, but you can not just go out and release your own version of "Born to be Wild" without paying royalties, the lyrics and music are both protected. If you change all the words and the music though its fine, of course it is now an original and would bear no resemblance to the song you are covering. This is assuming you mean recording the song if you mean just covering the tune live then you can play it note for note and are not even required to acknowledge the original author and there is nothing they can do about it.
