AI music is generally not going to be copyrightable unless they can show genuine human creativity was involved. So if a song is 100% AI, you could just go around performing it or straight up selling copies yourself and there's nothing* they could do about it. Though I do wonder if a human writes the lyrics, but AI generates all the music parts, if it becomes sufficiently human for copyright. Because the lyrics at that point would be actual creativity.

* I am not a lawyer, and this won't stop them from possibly trying to sue you or even winning depending on the situation. Or trying to prove there is human ingenuity involved. Do at your own peril.