The Big Question

The big question is: "What is Music?".

It seems an easy question to answer, because we are all so familiar with music. But being familiar with something is not the same thing as knowing what it is.

When I ask myself this question about music, I ask it as a scientific question. So I want an answer which relates music to our scientific understanding of the world. And I want an answer that makes predictions about music (and for bonus points, it should make predictions about other things besides music).