While there are other mediums of art, I think music is the purest form of it. Sculptors take a preexisting medium (clay) that is tangible and shape it into something else. Painters do this same thing except with paint. Music, however, takes a non tangible medium and creates something completely new out of it.
The music may be based on something, but it wasn't tangible at the beginning. A musician creates something out of complete nothing. While there are representations of the notes a musician uses, You can't touch or see the actual sound of notes.
Here's something that I'm listening to at the moment..