I’ve met a few people who work in very competitive finance fields with music degrees. It’s not common, but it’s all about can you pitch yourself to a prospective employer. Honestly man, as someone with a little more life experience, perhaps, a degree in mathematics can pretty much translate to anything. Having a minor, in music would be cool, if that’s what you’re into, but following college no one really asks what your minor, or concentration was in. I think keeping in mind job prospects is smart, but we’re all human, man. You have to do something you enjoy or you’ll go nuts later down the line. Is it impossible to get a major in math, and just keep piano/music as a way to escape the portions of school you don’t like, or just keep it as something inherently pleasurable to you? Hope that helps man.