We take the goal of a theory of music to be a formal description of the musical intuitions of a listener who is experienced in a musical idiom.
The result is a theory formulated in terms of rules of musical grammar. Like the rules of linguistic theory, these are not meant to be prescriptions telling the reader how one should hear pieces of music or how music may be organized according to some abstract mathematical schema. Rather, it is evident that a listener perceives music as more than a mere sequence of notes with different pitches and durations; one hears music in organized patterns.