Salon has an article about the "death of chick lit." I have a certain fascination with genre writing in fiction, less with genre as a commercial strategy and more with fiction that uses genres as surface topics — Joyce did it in Ulysses, Pynchon does it most brilliantly in Against the Day, China Mieville is perhaps the current reigning champ — but watching the product development and commercial markets in adventure, romance, westerns, space opera, fantasy, crime etc. rise and fall and sometimes return, even to challenge the "art" genres on their own terms is engaging on its own terms.
Music has its genre repertoires as well, and tracing them is of similar and probably more popular interest. Most musical production, the most popular music, is attached to genres with fairly hard boundaries between them. The kind of music I work with most — my own music, the music I discuss on this blog etc. — is marginal to this, when not essentially inaudible to audiences of critically mass. But for right and/or wrong, from this position of marginality, it's been a strategic conceit of serious/classical/avant-garde/modern/experimental music maker that we don't do genre proper, but rather reserve the right to use genre as a material and formal resource. Indeed the post-modernistas among us practically live off of genre-mining. But when our music does not refer to or otherwise partake of genres, we tend not to think of our output in any generic terms. The old masterpiece ethic of late classical composition is, in part, responsible for this with its insistence on total reinvention with each individual new work and a stubborn sensibility valuing the individual composer's brand identity and the consequent stylistic territoriality contributes to this as well. We think of our own musics, rightly and/or wrongly, as above, beyond, or aside from genre.
But the rest of the musical world sometimes pays attention and sometimes features of our music are appropriated as generic musical material. In some cases — Philip Glass's music is the best example — there is even a feedback loop at work in which the popular appropriation of elements of as figures and styles can be heard to affect subsequent music-making at the source. The imitations and parodies (in the old musical sense) of Glassiana in film and television theme music picked up on the tonal aspects of Glass's practice divorced from the acoustical residua and graffiti that made his music once so transcendent, and Glass himself gradually took a similar turn. In this manner, something very close to a musical genre has been developed and it is indeed now possible (it's happened to me, even) for a film producer to phone up a composer and ask for a package of themes and incidentals a la Glass. It has become a genre because it is recognizable, durable, divisible, and transportable (i.e. can be reproduced in varying musical contexts and functions) as such in the musical market place; a musical genre is thus, by definition, currency in the musical market.
Glass aside, as the serious/classical/avant-garde/modern/experimental is, in commercial market terms, marginal, if not dysfunctional or even failed, is it otherwise useful to talk in terms of genre? In fact, I think there are some niche markets in which it is useful, particularly as an historical aspect. The 12-tone or serial bebop piece, for example, had currency (in both senses) in a certain micro-market — largely academic — for a certain period of time. That era has long since ended* but some of those who had invested much in the technique and aesthetic managed — with a mixture of strategic reinvestments and tenured academic positions — to anchor themselves enough to sustain careers well into the next regime, if only as skilled artisans of an archaic practice, like mechanical watchmakers or specialists in the arcana of old computing systems.
* Free dissertation suggestion: The Break Down of Bretton Woods and the End of the Princetonian Twelve-Tone Ascendency.