A most excellent post. I think Ozfly and Unsound have summed it up nicely in saying (forgive me if I have misunderstood) that melody and rhythm are fundamentally understood by humankind and that a great deal of what we "really" appreciate in listening to or participating in music is based on our intellectual appreciation of the place of that music within our own musical history. I also like Gregm's comment that harmony is better understood as being what is "the correct sequence or correlation of things". I think that sense of the word harmony effectively differentiates "musical music" from "ordinary music" and noise. That which is most harmonious - that which is most correct in its sequence and correlation - is that which pleases us most. I am in the harmony as nurture vs. nature camp. I would cite African music as an example in that it runs on a different tonal scale (here I would disagree with Unsound in saying that the chromatic (I assume meaning diatonic) scale is globally accepted) and with an entirely different rhythmic base than western music (some would say arrhythmic but I would say multi-rhythmic) but even if westerners cannot sing along with it, anyone who grows up with African scales and rhythms finds it completely harmonious.
I am not certain that one piece of music would convey the same emotion to all people around the world who listen to it if they have not been subjected to it before. If someone can tell me/us who don't know, I would like to know if a song in an African pentatonic scale had a "minor" key interpretation in western music, would it have the same pathological and emotional meaning in Africa (and I'm sure I'm being overly broad here) as it does to those brought up in the western musical tradition?
Unsound, regarding art in equations... "art" in music is taking the pieces we already know and rearranging them in a way which makes us "see" something in a new way. I have to imagine that to serious mathematicians, there are few new building blocks but the ways of using them eloquently are still being discovered, and a new discovery which excites the senses and stirs the emotions is indeed a thing of beauty.
And I agree with Gregm that Detlof likely has something prepared for us... I, for one, am looking forward to it.