I have a theory that music is special because it is unusally powerful at allowing us to experience the emotions of another person. We find these moments in the clipping of a word, the changing color in a voice, or a pianist’s slowing rubato. And as listeners, we go: “Ah, I know how that feels like right there.”
Few other modes of communication seem to allow for this. It could be that music has infinite variations in pitch, timing, and timbre, which leaves it unconstrained by signifiers like words or symbols that require shared knowledge of their meanings. The complexity in music is mind-boggling enough that musicians often avoid actively focussing on any one mechanic for fear of sounding stilted.
It could also be that music is non-directed, in that its point isn’t that the listener receives, but that the performer expresses. This removes distortions from self-awareness or awareness of the communication.
Together, these elements paint a picture of a musician in performance: Conscious not of the audience, or the specific mechanics of the piece, but the fullest expression of themselves. So that when they modulate their sounds and realize one of the infinite possible variations, we the listeners can replay in ourselves the precise stirrings that created that gloomy lilt or soaring harmony and in doing so experience the feelings of the musician through the music.