music , mind , thought and emotion

There is not a society on this planet, nor probably ever has been, which is without some form of musical expression, often closely linked with rythm and dance. My question is less concentrated on the latter two however.
What I am pondering boils down to:
What is music and what does it do to us
Why do we differentiate music from random noise so clearly and yet can pick up certain samples within that noise as musical.
By listening to music, we find some perhaps interesting, some which we would call musical. What differentiates "musical music" from "ordinary music" and this again from "noise"?
In a more general sense again:
If music has impact on us, what is the nature of our receptors for it. Or better: Who, what are we, that music can do to us what it does?
What would be the nature of a system, which practically all of us would agree upon, that it imparts musicality best?
And finally, if such a sytem would exist, can this quality be measured?