There's a lot of research in acoustics. You could look into that.
I'm considering doing a joint honours degree in Mathematics and Music.
I guess the reason I'm wanting to do this degree is because like millions of other hopefuls, I have a stupidly strong desire to build a career/lifestyle around music, but I'm also trying to be realistic and take into account my need to eat and have a roof over my head - plus I'm pretty cool at my maths.
So I ask you, are there any niche job areas which require a strong knowledge of both music and mathematics, or am I going to end up working as an accountant with a weekend band and stupid thoughts of it ever going anywhere.