few years ago, I tried out Pandora, the "Music Genome Project" for Internet radio. You tell them a song you like, and they stream over the Internet to you other songs that share similar musical elements, as rated by their staff of professional musicians for about 250 factors. It's not a recommendation system where people who share your tastes tell you what they like, it's based on the actual musical content of the songs.

I found it worked pretty well. But one response was off: I put in Revolution Rock by the Clash, which isn't a rock song at all, but a lazy, joyous reggae ramble. Pandora came back with the punk Career Opportunities by the Clash, which suggests that one of their employees had cut corners and categorized Revolution Rock by title rather than by music. I sent in an email pointing this out, and got a detailed apology from Pandora's CEO, suggesting to me that maybe the boss had too much time on his hands to write to his customers (who weren't paying him, anyway).

So, I'm glad that they've survived financially. Now, there's a long article in the NYT Magazine, "The Song Decoders" by Rob Walker, about how Pandora works:

[CEO Paul] Westergren maintains ”a personal aversion” to collaborative filtering or anything like it. ”It’s still a popularity contest,” he complains, meaning that for any song to get recommended on a socially driven site, it has to be somewhat known already, by your friends or by other consumers. Westergren is similarly unimpressed by hipster blogs or other theoretically grass-roots influencers of musical taste, for their tendency to turn on artists who commit the crime of being too popular; in his view that’s just snobbery, based on social jockeying that has nothing to do with music. In various conversations, he defended Coldplay and Rob Thomas, among others, as victims of cool-taste prejudice. (When I ran Bob Lefsetz’s dismissal of Pandora by him [for responding to a Jackson Browne song with a Journey song], he laughed it off, and transitioned to arguing that Journey is, actually, a great band.)

He likes to tell a story about a Pandora user who wrote in to complain that he started a station based on the music of Sarah McLachlan, and the service served up a Celine Dion song. ”I wrote back and said, ”Was the music just wrong?’ Because we sometimes have data errors,” he recounts. ”He said, ”Well, no, it was the right sort of thing – but it was Celine Dion.’ I said, ”Well, was it the set, did it not flow in the set?’ He said, ”No, it kind of worked – but it’s Celine Dion.’ We had a couple more back-and-forths, and finally his last e-mail to me was: ”Oh, my God, I like Celine Dion.’ ”

This anecdote almost always gets a laugh. ”Pandora,” he pointed out, ”doesn’t understand why that’s funny.”

When I started up Pandora again for the first time in years, it remembered all the songs I had entered years before and set up "radio stations" based on each one. Here are some examples of what it came up with in response to my suggestions from the 1975-1990 era. Keep in mind that Pandora doesn't seem to play songs in order of similarity to the source song. It just picks a bunch of songs that are kind of like the one you chose and then it shuffles them. So, each time you return, it offers you somewhat different songs.

Something I hadn't expected was that Pandora performs a sort of factor analysis on your musical tastes. Listening to these songs that I picked out a few years ago plus other ones similar to them, I would say I have post-British Empire upper middle class public schoolboy tastes in music. This may seem odd, but my tastes in songs would seem most natural for a Scottish or northern English lad at a southern English boarding school for toffs, or maybe at Sandhurst, the military academy. I'm not saying that's what people of my generation like that actually liked, just that it would make sense.

Very strange, but it also fits a lot of my taste in authors as well (Waugh, Orwell, Wodehouse, etc.). I now remember how much I liked David Niven's autobiography, who was a Sandhurst grad. And the autobiography of Churchill, another public schoolboy / Sandhurst man.

So, it's no surprise that The Clash were always my favorites. After all, Joe Strummer, despite his appalling teeth, was an upper middle class public schoolboy whose dad, a friend of Kim Philby's, was a diplomat (i.e., spy) for the fading British Empire.

- Steve's Pick: Death or Glory - The Clash ("But I believe in this and it's been tested by research" — What better lyrics to try out Pandora upon?) - Pandora's #1 response: Queen Bitch - David Bowie A very Lou Reed-like electric guitar riff rocker. I guess it points out the influence of Reed on The Clash as well as on Bowie. Still, the Bowie song is missing the inspiring masculine militarism of Death or Glory. Ultimately, David Bowie and Joe Strummer are different personalities and will appeal to different listeners. - Pandora #2: Career Opportunities - The Clash Well, that wasn't too much of a stretch! But it does raise the issue that Career Opportunities isn't quite as good as Death or Glory. The Clash had already done a bunch of songs like Career Opportunities, and they weren't putting more basic punk rock songs like that on their London Calling album. Death or Glory, as the title suggests, was intended to top their earlier stuff, or go down in flames.

- Steve: Story of My Life - Social Distortion (Scots-Irish-American roots rock anthem, both self-pitying and uplifting, much like Death or Glory) - Pandora #1: Death or Glory - Social Distortion I guess I should have seen this one coming! - Pandora #2. Sunday Morning Coming Down - Me First & the Gimme Gimmes A Scots-Irish rock cover of the fine Kris Kristoffersen song made famous by Johnny Cash — I'd never heard of the band but I liked it a lot.

- S: The Great Curve - Talking Heads (from their Afrobeat groove era when they had 9 musicians) - P1: Waiting for the Roar - Fastway Pretty good AC-DCish metal, but not at all like Remain in Light-era Talking Heads. - P2: Misfit Love - Queens of the Stone Age This is a grunge groove song that has some similar elements to the Talking Heads song, but is much heavier and less lilting.

- S: In Between Days - The Cure - P1: A Night Like This - The Cure For English heterosexual foppish romanticism, you can't beat The Cure. On the other hand, once again, while A Night Like This resembles In Between Days, it isn't as good. - P7: I Melt With You - Modern English This has always struck me as the closest predecessor to In Between Days. Perhaps Pandora isn't set up so that the closest match is the first song played?

- S: Heroes - David Bowie (with Brian Eno) - P1: Space Oddity - David Bowie I suppose there's some underlying chord structure similarity, but the gestalt is radically different between the acoustic guitar Space Oddity and the shimmering Wall of Synths of Heroes, but then Heroes is a pretty unique artifact. Offhand, I can't think of any songs that Heroes is like. (Holidays in the Sun is also about the Berlin Wall, but not very close musically). - P2: Bad Girls - Don Felder (of The Eagles) Nah ... - P4: More Than This - Roxy Music Great languid song, although I'd probably put it on my In Between Days Fop Rock station (see above). One thing you learn as you see songs show up on one of your stations that you think are more like the source song for a different station is how related all your songs are. For example, on my Veronica station below, Pandora played a song I had never heard before, Shut Your Eyes by the Shout Out Louds, which sounds just like a more straight-ahead, less shimmering version of In Between Days.

- S: Revolution Rock - Clash (joyous reggae) - P: Too Late to Turn Back Now - Don Carlos (happy reggae cover of the soul song by Cornelius Brothers and Sister Rose) Good choice. This is the kind of thing I would never find by myself.

- S: Genius of Love - Tom-Tom Club (offshoot of Talking Heads) A fun dance song - P1: Mystereality - Orchestral Maneuvers in the Dark Nah - P2: Space Is Deep - Hawkwind Nah

- S: Veronica - Elvis Costello (w/Paul McCartney) - P: Takin' Me Back - Cheap Trick I was a big Cheap Trick fan in the 1970s, so this is a pretty good call. Most of the recommendations on this channel are conventional rock songs, but lack the expertise that McCartney brought to Costello in 1988. (I've always thought that the dyspeptic Costello was McCartney's best possible replacement for John Lennon in terms of pushing McCartney to repress his kitschy side. If McCartney had teamed up with Costello in 1978 right after Costello's first album, who knows how good they could have been together.)

I think that's a basic problem that you can't get around in Pandora: if you like a song not so much because of the style but because it's an expert execution of a style, then Pandora isn't as good as a recommendation site.

Overall, I think the above examples are a little unfair to Pandora, since there isn't a notable dropoff in correlations as the songs go on. Possibly they randomly mix the order of the songs in terms of similarity so that listeners don't get progressively more displeased as they go.

It would be interesting to use Pandora's remarkable database for scholarly purposes. For example, T.S. Eliot pointed out that an artist creates his own "school" of predecessors that nobody noticed had anything in common before. For example, I've always felt that the ancestors of the punk rock of 1976 included from the 1968 to 1973 era: Communication Breakdown by Led Zeppelin, Paranoid by Black Sabbath, and Saturday Night's All Right for Fighting by Elton John, three songs that sounded like they have more in common after you'd heard the Ramones, Sex Pistols, and Clash than before. This giant proprietary database would presumably allow those kind of academic hypotheses to be tested objectively.