Cavemen spoke long before they learned to write. Like ancient pictographs, early written music was in the form of shapes, surviving today as mordents and gruppettos. The goal was to remind the performer of the tune they already knew. Today’s written music conveys such a wealth of information that you can do a sufficiently accurate performance without ever having heard the piece, but there is still a gap between what it tells you and what you say with it.
Music is in the ear of the listener, which is to say that music can be defined as how the brains in the audience interpret inputs. That makes it a function of the listener’s life experience and acquired skill. It is cast in the context of whatever cognemes are consistent with the listener’s construction of the world. In other words, it is a form of communication.
More than that, however, music is in the generation of what goes to the listener’s ear and thence to the brain and personal world view. It is the feedback between the performer’s ear and their mouth and fingers. That’s not a chicken and egg situation, however, since there are deaf musicians. It is not in the muscles but in the intersection of finger and instrument, of breath and larynx.
In short, I’m saying music is the act of making sound rather than the sound itself. What you imagine in your mind and instruct your instrument to do, and what actually comes out, are both approximations.