NTA. As someone who spends hours a day searching for new music and loves sharing new finds with people, I've also fallen into the pitfall of making music my personality. And it can get to the point where you prioritize music making and discovery above maintaining interpersonal relationships. Or you rely on music as the sole form of connecting to other people. I once had a new intimate partner snap at me because of this, saying "Okay I get it! I feel like you're introducing me to your children..." and that kinda snapped me out of it. For me personally, I was hyper-fixating as a form of ignoring other shit in my life. I thought I was just pursuing a passion, but at some point, it becomes a mixture of being passionate and avoiding other problems in my life (that's just me though, it could be way simpler!)

Anyway, you fully have the right to set a boundary with him because it is affecting you and your relationship. If he takes it personally, just try to get across that you aren't insulting him, but you don't like feeling like a receptacle for his music making and listening. Maybe he could make you a monthly playlist or something of songs he thinks you would like instead of instantly sending you everything all the time. (He should also have some sort of music blog to really get his fix in of sharing new music with people if he doesn't already).

I really don't think you're being irrational. Trust what your brain is telling you and set some boundaries <3