Very chill game, made me realize I don't recognize WASD when I see it spelled out compared to just direction arrows lol.
I would have liked to see the difficulty ramp increase a bit sooner, maybe if there were interesting ways to increase score you could tie the spawn rate and patterns to that. One of the more enjoyable ways to play score attack games for me is when hitting multiple targets at the same time gives a bonus to score, maybe allowing the screen to fill with multiple asteroids that have the same key or chaining multiple asteroids in a row could achieve this.
I couldn't figure out the purpose of the sphere of music beyond obscuring nearby asteroids which was a lame ending to my run just as it ramped up.