I stumbled across The Music Business and the Big Flip by Clay Shirky. In it, he notes how the music industry has been transformed by digital technology “at the ends” — in the studios and in the way listeners use it — while noting that the “middle” hasn’t yet seen so much effect.
He notes how quickly aggregate filtering has caught on with regards to written material, with collaborative sites like SlashDot and Kuro5hin as well as meta-indices like Blogdex. He wisely makes no predictions about when music might start to get similar treatment, but does a good job of pointing out similarities and differences between music and writing. Check it out.