Is music just sound? Just colourless specks of air going back and forth?

Sound is the air dancing. The hand motion you make to conduct music more or less mirrors exactly what the air is doing. Music is a harmonious dance. Rather, music was always dance first, music second. 

Music feels like something. The harmony of music is mathematical. Properly appreciated, math feels like something. A good, true equation is a form of music, and if you understood it, it would feel like music. Music is a way of showing you what 2+2 really feels like without having to properly understand it first. Daoist mobius dualism: the point of the lunar path is to lead you to the solar path. (And then, in turn...) Teaching math properly involves playing you the songs you're working with.

There is a truest and thus most holy statement. One form of it is this: 0 = 0. Looks plain, at first. Just a single note? Isn't.