But some theories about music are very mathematical. We probably are just beginning to understand how to think about music in terms of math, because music is complex and (at least much of Western music) discrete. An article in Science in 2008 defines equivalence relations and uses n-dimensional symmetries to describe sequences of pitches in time. See here: http://www.sciencemag.org/content/320/5874/346 and here: http://www.sciencemag.org/content/320/5874/328.full)
I think there is some truth in a Leibniz quote: "The pleasure we obtain from music comes from counting, but counting unconsciously. Music is nothing but unconscious arithmetic." (http://www-history.mcs.st-and.ac.uk/Quotations/Leibniz.html)
It's hard to say why I like Radiohead. At first I really didn't like them; I found Kid A (album) especially discomforting. I had to let go of a lot of pre- (mis?) conceptions about what makes music good before I could come to like it. I probably had to let go of a lot of pre- (mis?) conceptions about myself and my worldview at the same time to appreciate the lyrics. But now it's one of my favorite works of art.