Sure, you can model music composition as a RL task. The AI composes a song, then predicts how much a human will like it. It then tries to produce songs that are more and more likely to be liked.

Another interesting thing that alphago did, was start by predicting what moves a human would make. Then it switched to reinforcement learning. So for a music AI, you would start with one that can predict the next note in a song. Then you switch to RL, and adjust it's predictions so that it is more likely to produce songs humans like, and less likely to produce ones we don't like.

However automated composition is something that a lot of people have experimented with before. So far there is nothing that works really well.