How Pandora Works

Pandora is certainly a wonderful service. You pop in a song or artist you like and just like that it plays a song by a group that you never heard of but you love. Its like magic, but behind the scenes there is a ton of stuff going on. More, in fact, then you could ever have imagined.

What became of it all? Something some would call neo-radio. Pandoras tagline is simple but descriptive: Its a new kind of radio stations that only play music you like. It seems to be a pretty good job of it too. But how does it mange this so well?
Back in late 1999 a man, Tim Westergren sent out a call for graduate students wanting to analyze music. Nolan Gasser, who held a masters degree in composition, and a Ph.D. in Musicology immediately answered. Westergren realized quickly that Gasser, who had been playing instruments since age four, and composing since eight, was not only capable of analyzing music, but also of help Westergren realize his dream: to create what would come to be called The Music Genome Project. The the idea was to create a database of attributes for songs so that a user could find new songs based on the attributes of songs they liked. Simple on paper, not so much in practice.

The Music Genome Project is the backbone of the Pandora Service. Westergren and his employees came up with several hundred  musical genes that a particular song could have. These include more easily understandable ones such as danceable grooves, and acid rock qualities to more technical ones such as chopped & screwed production and extensive vamping. Every single song in Pandoras database (of which there are some 800,000) was hand analyzed and assigned the appropriate musical attributes. Each genre has a particular set that are used. For example, Rock and Pop songs have about 150 genes, Rap songs have about 350, and Jazz has about 400. Each song is analyzed by one (or sometimes more) trained professionals, many of which have a advanced degree in music. Each gene is rated in a scale of one to five in half integer increments to indicate how much the gene is expressed. A single song generally takes 20-30 minutes to complete, but some, like classical pieces, can take an hour or more to analyze.

How it all comes together

When you type in a song on Pandora, several things happen. First, Pandora searches for your song in its database. Every song has a vector associated with it that indicates the rating of each of the genes. It then searches for songs that have similar qualities and adds them to the playlist. Unlike many other music suggestion services, such as, Pandora does not take genre into account when selecting songs. Although, because songs of the same genre tend to have similar attributes, many if not most of the songs played will be of the same genre as the song you inputted. If you input an artist, Pandora will select a song from their discography at random match that song. The problem with this is that, because you have no choice over the particular song, Pandora may very well select a song you dislike, and play more songs like it. For this reason, many people suggest using songs to create stations if you want to get the most out of Pandora.

Like it or dont

Another very important aspect of Pandora is the thumbs up/thumbs down feedback system. This allows users to tell Pandora if they like a song, or if they dislike a song. If you give a song a thumbs up, Pandora will play more songs like the one you just gave the thumbs up to. If, on the other hand, you give a song the thumbs down sign. Pandora will play fewer songs similar to the one you gave it feedback on. This allows for a high degree of customizability. Pandora pulls data on songs from all of your stations, not just the current one, so songs thumbed up in your Foo Fighters radio will be taken into consideraton when you listen to your U2 radio (assuming, of course, you have two radios like that).

Pandora is free, but this gives you an ad supported version with only 40 hours of listening a month. There is a payed version of it, but I think 40 hours with a 30-second (or less) ad every now and then is pretty good for a free service. And, for now, that it how I intend to use it. Although it is not currently available outside the US, perhaps, someday.

Im had a great time peaking under the hood of this awesome service. I hope you enjoyed learning about it as much as I did.

Do you use Pandora? What are your experiences with it? Did I get something wrong? Feel free to leave me a comment below, or send me an email.