I think it goes both ways. Historically, most music theory has arisen after the fact to explain why music written a hundred years before sounds good. However,

I think it goes both ways. Historically, most music theory has arisen after the fact to explain why music written a hundred years before sounds good. However, it is possible to discover some particular mathematical structure in music and then generalize to create new previously-unknown forms of music. There's a certain degree of artistry to this, so it's hard to say where the science ends and the art begins. To an outside observer it may look like someone just randomly made noise until something "worked". Personally, I think western music is stuck in a 12-tone-equal-temperament rut. It's not as if we've discovered all possible 12-TET music, but it's getting harder to find anything truly novel harmonically or melodically. (Timbre and rhythm are still good ways to innovate within 12-TET.)