Pandora's (Music) Box.

This is interesting - from arts critic Terry Teachout:

"I’ve been playing with Pandora, the new Web-based streaming audio "music discovery service." Based on a week’s worth of hands-on experience, I’ve decided that (A) it works and (B) it’s going to be a Very Big Thing. To use Pandora, you start by inputting the name of a pop artist or song that you like. This creates a “station” that you can “tune in” on your computer at will. The station then plays a record by that artist, followed by similar-sounding songs by different artists. You respond in turn by telling Pandora whether or not you like each song it plays. At any time you can input additional artists or song titles, which automatically increases the size of your station's playlist. The more information you supply about your tastes, the more accurately Pandora can analyze them and select new songs you’re likely to enjoy...

Believe it or not, this isn’t just hot air. When I “asked” Pandora why it was playing The Band’s “Look Out Cleveland,” for instance, it responded as follows: “Based on what you’ve told us so far, we’re playing this track because it features country influences, a subtle use of vocal harmony, mild rhythmic syncopation, acoustic rhythm piano and mixed acoustic and electric instrumentation.” All true. Of course, it was also playing "Look Out Cleveland" because I’d already told Pandora that I liked The Band, but the very next song it played, Albert Lee’s “The Victim,” contained the same musical features, and I liked that one, too.
Once I’d inputted the names of a dozen artists and given thumbs-up and thumbs-down responses to the songs Pandora was playing in response, it became clear to me that the analytic algorithm it uses to choose new songs was sufficiently sophisticated to second-guess my musical tastes with an accuracy that bordered at times on the eerie. As I write these words, Pandora is playing me Frank Sinatra’s live recording with Count Basie of “The Shadow of Your Smile.” Why? Because it features “swing influences, smooth vocals, romantic lyrics, a horn ensemble and” (wait for it) “acoustic guitar accompaniment.” Sure enough, Freddie Green’s rhythm guitar is very prominent in the mix on the Sinatra-Basie recording of “The Shadow of Your Smile.” Needless to say, that’s not a detail a casual listener would be likely to notice, but it happens to be one of the aspects of this particular recording that I find most engaging.