How Pandora Radio Works

And what are some of the musical traits of Ben Folds' songs? To let us know, Pandora chooses a Ben Folds song at random and plays it for us. In the bottom portion of the player, we can see how the Music Genome Project has characterized this particular song (see above). The next song the station plays will share some of those traits. In this case, it's "Amsterdam" by Coldplay.

Pandora automatically displays the Music Genome traits for the first couple of songs our new radio station plays. After that, we can find out exactly why Pandora is playing any song by clicking on the album art and choosing "Why did you play this song?" from the menu. After "Amsterdam," Pandora plays Ben Jelen's "Give It All Away." Let's find out why.

You probably notice in the above image that the trait description begins with "Based on what you've told us so far." It's not just talking about the fact that we like Ben Folds. Pandora wants us to give it feedback so it can refine the station based on our likes and dislikes. We can give any song the station plays either a thumbs-up or a thumbs-down, and providing this feedback instantly changes the station's playlist. Let's say we don't care for "Give It All Away." To give it a thumbs-down, we left-click on the album art and chose the thumbs-down, "I don't like it" option.

Now Pandora will never play "Give It All Away" on our Ben Folds Radio station again, and it will play songs that are genetically similar to "Give It All Away" less often. If we click on the arrow next to the Ben Folds Radio station and choose "Edit this station," we can see that Pandora has put "Give It All Away" on the list of songs we don't like.

Giving a thumbs-up has the opposite effect -- that song and other songs like it will play more often. The idea is to continually provide feedback so the station learns more and more about what we like and don't like. The result is a progressively personalized radio station that really does play only music we want to hear. It takes a while to get there, but most people agree that the feedback process works. Some of the other things we can do with Pandora include:

There's a lot going on with the Pandora player, but it's all pretty easy to access once you get the hang of where the clickables are. Next, we'll take a look at what's happening behind the scenes of the Pandora experience.

The Pandora player is a free, Web-based Flash application. You don't need to download anything to use it as long as you have Flash 7 or 8 installed on your computer. The only difference between the free service and the subscription service ($36 per year or $12 for three months) is the ads in the free version. Everything else is the same.

Pandora delivers a 128-Kbps stream of music, and it only works with a broadband connection. It derives its music license from the DMCA (Digital Millennium Copyright Act of 1998) guidelines for streaming Internet radio, and the digital rights management (DRM) scheme it employs is notable in a few ways. First, Pandora will never play a specific song on demand; if you add a song to a station, it will show up eventually, but Pandora can only work it in at random. Also, you can only skip 10 songs in an hour -- this is so you can't just skip to the song you're looking for. The license also limits the number of times Pandora can play a particular song or artist in a particular time period, and to this effect Pandora stores a list of the songs played on your station in your computer's Flash local storage so it knows what it has played already. It also stores your user data there so it recognizes you when you arrive at Pandora.com.

Probably the most interesting stuff going on behind the scenes has to do with the Music Genome Project that Pandora taps into. Unless you've got a degree in music theory, most of the Genome's terms of analysis are outside the realm of common usage, but it's still cool to check out some of the parameters it's using to determine which songs are genetic matches for your seed song or artist.

The Music Genome is not a single, homogenous set of traits. Different types of music require some different subsets of genes. There are four basic groupings within the Genome: pop, jazz, rap/hip-hop/electronica and world. According to Music Genome Project founder Tim Westergren in a Tiny Mix Tapes interview:

Speaking of profanity, an interesting side note: Pandora only plays the explicit version of songs. The people at Pandora discussed it at length and decided to stay true to the artists' original intentions. When you register for Pandora, you need to provide your date of birth, and maybe that's part of the reason why.

In the next section, we'll take a look at how the Pandora playlist is assembled.

So here's what happened behind the scenes when we created our Ben Folds Radio station: Pandora located a song by Ben Folds and pulled up the Genome analysis for that song. It then ran an algorithm that compared every song in the Genome database to the genetic makeup of that song in order to identify songs that have similar traits. The algorithm looks for matches across 400 parameters. Here's just a handful of the traits and concepts it looks at (definitions excerpted from the Virginia Tech Multimedia Music Dictionary):

Keep in mind here that every song's traits are determined "by hand." There was an actual human being who identified the characteristic voice types, beats, structures and tempos for each of the 400,000 songs in the Genome database. It's a profound undertaking that will probably continue for as long as Pandora Media has the money to pay its experts to listen to music all day.

We'll take a look at some concerns with Pandora in the next section.

There are, of course, concerns about the Music Genome Project from some in the music world. First, since the Genome is proprietary, there's no possibility for independent review. For all we know, Pandora Media's "experts" don't know the difference between syncopation and vamping. Also, in a much broader way, the Music Genome Project assumes that music's traits can be objectively analyzed at all -- that the mind of the listener can be left out of the equation. Some experts doubt that music can be quantified in this way.

Regarding the player itself, an issue arises when you create a station using an artist like The Beatles as the seed. Some artists have such a varied collection of styles that there are endless ways the Genome algorithm can go when determining matches. In such a case, Pandora may return music you don't like at all. For instance, if you love the Beatles' later stuff like "Across the Universe" or "I am the Walrus," you'll probably be disappointed if Pandora returns music that's similar to "I Want to Hold Your Hand." For this reason, it's often wise to use a song instead of an artist as a seed.

With all of Pandora's attractive features and novel approaches to personalized radio, it does tend to wow people when they discover it. But wows don't pay the bills, and Pandora will have to bring in real cash if it's going to survive. In the next section, we'll find out how Pandora plans to turn the academic Music Genome Project into a commercial commodity.

The Music Genome Project and its accompanying user interface are not exactly the first of their kind. Music producer Alan Lomax, best known for his work in the 1950s and '60s with BBC radio and folk artists like Woodie Guthrie, Lead Belly and Pete Seeger, spent 30 years developing an interactive music and dance "jukebox." Lomax's Global Jukebox makes social, cultural, historical and regional connections between various art forms. The connections are based on a Genome-like analysis of musical traits and dance moves combined with a database of cultural characteristics throughout history. According to Slate.com's Martin Edlund in "The Madonna Code," the Global Jukebox can tell you that "a high-energy vocal style correlates with the presence of dairy in a society's diet." In "Alan Lomax's Multimedia Dream," Michael Naimark reports the connection between "dances with narrow heel-to-toe movements" and "societies whose main crop is planted in narrow rows (like rice)." The Global Jukebox prototype is currently stored on an Apple Quadra in New York City's Lomax Archive. Many corporations expressed great interest in the creation, but none followed up with a commercially viable use for it.

So how does Pandora plan to turn academic analysis into cash? Approaching the question from a theoretical standpoint, Pandora's potential commercial success is based on an economic concept called the "Long Tail." In the digital age, where consumers can easily find the specific thing they're looking for and producers can easily provide new content for distribution, Long Tail states that directing consumers off the beaten path is a potential key to profitability. In practical terms, Pandora's current revenue model seems to involve placing advertising in the free version (no ads in there as of May 2006), charging subscription fees for the ad-free version (as of May 2006, about 15 percent of subscription revenue goes to maintaining Pandora's music license and buying bandwidth) and sending users to iTunes and Amazon to buy the music they hear on Pandora. Pandora Media also licenses a commercial version of the music-discovery service to music sellers like Best Buy, Tower Records and AOL, who use it to recommend new music to their consumers at kiosks. According to the Pandora FAQ, what the company won't do is sell their objectivity. In the company's words, "We will never, ever take money to play a song or analyze it favorably on Pandora." So selling airtime is probably out.

If Pandora is going to be a real commercial success, it will have to compete with music giants like iTunes. Pandora already has teamed up with an electronics company to create a piece of hardware that releases Pandora from your computer, similar to what Apple's AirTunes does with iTunes. The Slim Devices Squeezebox plugs into a home network to stream Pandora from your computer and control it from anywhere in your home. And Pandora Media is already talking about taking Pandora mobile in the form of a standalone player and an application for devices like cell phones and PDAs. Gift subscriptions are in the works, and as soon as Pandora can work out the international licensing agreements, the service will be available outside the United States.

For more information on Pandora and related topics, check out the links on the next page.