I have composed a definition of music which suits my tastes, and which I find sufficiently minimalist to be 'true':
"Music is anything for which there is an active listener"

My feets on the snow, the music of the street, the latest mp3 from brothomStates, or the current number one in the charts are all Music.

now please bear in mind that this definition is a definition for music, not for art, which is different thing: the music of the street often doesn't have any artistic value, although musically enjoyable.