No, don't ask him if you think that music is more important than you. That would just be a challenge for a fight. Tell him that sometimes you feel he does not pay you the attention that you deserve. I know how strong the feeling can be, 'him thinking your a mistake', thats a terrible feeling. But on the other hand, if you are special to him he should make an effort to understand how you feel.
Also, there is an important question you need to ask yourself, not him. "Am I getting what I need out of this relationship?" It is a very hard question to ask, but I think you already know the answer and your avoiding it. If he thinks about you as just a young muse, and plaything then your better off without him. If he cares deeply about what is best for you, and tries to understand you like he would the music that he loves then he will make the effort.
I worry for you that he is doesn't take seriously the feelings you have inside and how important they are to you, and how scared it makes you. Express yourself, if he is a loving man and one you deserve, then he will respond well.
There is always some madness in love. But there is also always some reason in madness.
-Friedrich Nietzsche
In every real man a child is hidden that wants to play.
-Friedrich Nietzsche