" Criticism is exciting just because there is no formula to apply, just because you must use everything you are and everything you know that is relevant, and that film criticism is particularly exciting just because of the multiplicity of elements in film art."

Pauline Kael, 1963

The last bit applies just as well to pop music, since the  music is only one element in the pop (or rock for that matter), so there's an embarrassment of perspectives from which you can approach the object of scrutiny