"My business is to sing."
I recommend Denis Dutton's The Art Instinct, a concise, accessible, and compelling overview of evolutionary psychology as it applies to the origins of the arts (the NYT review is here). The basic argument is that artistic interests and pursuits are universal to human experience (although with obvious temporal and geographic diversity) and are grounded in dispositions formed over a million years of hominid evolution.
Dutton's approach is nuanced and respectful of the gaps in our knowledge (theories of evolutionary psychology are far harder to demonstrate than are general evolutionary theories because, for one thing, brains don't fossilize). We do not, obviously, explicitly approach the arts in evolutionary ways any more than we consciously seek out a high-fat diet because it protected our ancestors from famine; the motivations in each case are quite literally unconscious.
In addition to general theories he handles the major arts individually. He maintains that all else being equal, people prefer depictions of landscapes that have basic features--a slightly elevated view of juxtapositions of open space and vegetation, signs of water, and small groups of animals and figures--of the African savanna in which humanity evolved. Narratives of all kinds (from Shakespeare to soap operas), Dutton claims, are natural ways of navigating the extreme complexities of human social life in a way that doesn't risk real-life consequences. Linguistic aptitude also can attract potential mates, although less so perhaps than impressive upper body strength (not all of us were blessed with both).
Music is clearly important to Dutton personally, and he acknowledges that it poses the greatest challenge to evolutionary theory inasmuch as such an abstract art does not, compared to other arts, seem as relevant to past survival advantage over evolutionary time. He ends up concluding that even more than the other arts, music is much like the peacock's tail, that is, a very contingent concoction designed to woo potential mates (witness the predominance of love as a perennial musical theme).
He also points out that compared to other arts, we tolerate and even invite an astonishing amount of repetition (albeit with variation), both of tonal ideas within musical works and of musical works themselves (over a period of years one might listen to a favorite album a hundred times, which we're not likely to do even with a poem). Let's see, what other human behavior involves the appreciation of extreme repetition with variation? Well, nothing comes to mind here, I'll think of it later.
Dutton takes clear aim at modernism in the arts (particularly atonal music and some avant-garde follies of the visual arts) as a misguided notion that taste can be culturally contorted to an infinite degree; rather, evolution suggests that our interests, while quite manifold, are finally finite. Indeed, avant-gardism over the past century has arguably been a massive expression of cultural hipsterism, in which mere exclusivity (manifested in the sheer cost of works of art as well as the smug satisfaction of being counted among the cognoscenti) has carried some sectors of the arts well into the realm of sophisticated kitsch.
The most hilarious example of this is best captured in Dutton's words:
The imitations reached rock bottom in 1961 with Merda d'artista, a series of works produced, in every sense of the word, by the Italian conceptual artist Piero Manzoni. In fact, in 2002 the Tate Gallery paid $61,000 to add to its collection Can 004 from Manzoni's series of ninety cans of his own feces...In Manzoni's case the only humor to be found is in the messy fate of many who acquired works in the Merda d'artista series: quietly, but knowing exactly what he was up to, Manzoni had improperly autoclaved the cans. At least half of those bought by museums and collectors eventually exploded.
In the closing pages of his book Dutton argues that great art relies on authentic individuality against a cultural background of stable values and the sense that some things do ultimately matter. This may be why the ironic age has found contemporary masterpieces to be hard to come by.
I find these kinds of evolutionary accounts to be fascinating and, really, deeply spiritual inasmuch as the fact of consciousness (and the necessary supposition of free will that comes with it) shields us from reductionism. Sure, one can say that Beethoven manipulates merely primitive urges just as one can say that tones are merely compression waves conveyed through air, but to do so is to miss the point. So much is both given and contingent, but the question in the arts, as in life, is: where do we go from here?