The closest music comes to 'theory' in the sense of the word that you're describing to describe music as a limited application of set theory.

Music theory not a theory in the scientific sense. It is not something that is used after observation to create a hypothesis that is then tested and if possible refined and retested until results correspond to observed reality, adjusting hypothesis and theory along the way. Music theory does not result in new music discoveries of underlying musical truths that have always been there awaiting discovery.

Music theory is a pretentious term, because it merely refers non-music abstractions of music --that is music theory is words, symbols, diagrams, etc-- that are used to describe music. That's all. Basic music theory with a limited vocabulary usually starts by teaching how to discuss rhythm and frequency. Advanced music theory vocabulary gives one the ability to discuss the structural elements of a composition with considerable precision.

Music literacy is very similar to linguistic literacy: basic symbols are combined to create larger words/phrases, which are themselves combined to convey even larger ideas. That's music theory: mental model, vocabulary, and symbols used to describe music in ways other than creating it.