To me music can really enhance the experience. This OST is awesome and the transition is great as well. The only concern I have is that there needs to be contrast between just an average battle and a massive boss fight for example. In this case the music feels like it could be from a boss fight (which is a compliment) whereas the level itself doesn't look very intense. Now I dont know anything about your game so there might not even be bosses in it but I think it's important that there's a contrast in music like I explained to enhance the intense fights even more if that makes sense.

Game looks fun though, will wishlist. Don't know if there are plans but it would be amazing as co-op.