Photo by Nick Vlcek

Thirty-three-year-old Josh Rosenfeld isn't just the prototypical indie-rock kind of guy—white, lanky, hoodie-wearing—he's an über–indie rocker. As the co-founder of Barsuk Records, he's helped launch the careers of Death Cab for Cutie, Nada Surf, and Menomena. He'd probably be the first person you'd go to for recommendations about new music—if he weren't so frazzled about the whole thing himself.

"Right now, as we talk, I have 30 CDs sitting on my desk that have been sent to me, in many cases by people whose taste I trust. But I just don't have time. There's way too much music to absorb," says Rosenfeld. "There's no way in hell I could do it."

If Rosenfeld can't keep up, what chance do the rest of us have? The digitization of music has caused its availability to explode, as entire albums can be recorded, uploaded, and transmitted around the world in a single day—to say nothing of individual songs. The result? Anyone online has a seemingly unlimited supply of new music.

"That's great in a way," says Rosenfeld, "because it's very democratizing, but it's also a disaster from the perspective of the paralysis that ensues from that much freedom of choice."

So if you wanted to learn about new music, where would you even start?

The Internet, which has largely been responsible for this torrent, is now attempting to solve the problem it helped create. The perfect music-recommendation technology is equally tantalizing for music listeners and makers. If the computer could figure out just what kind of music we'd each like, labels and bands would know who would be most receptive to their music, and listeners could blissfully discover one new favorite band after the next. Labels certainly need something to happen: Industry data-gatherer SoundScan reports that so far in 2007, overall album sales, which include digital downloads, are 10 percent behind 2006, with 118 million albums bought, versus last year's 131 million.

There has got to be a way to cut through the noise. And naturally, it started with a Belgian computer scientist.

In 1989, Pattie Maes moved to the U.S. from Belgium, her home country, with her Ph.D. in computer science, and wanted to find new music that she would enjoy. She transferred from the artificial intelligence department at MIT to the university's Media Lab, where she helped develop Firefly. Originally known as Ringo, it sought to automate word-of-mouth music recommendations. Early users e-ranked 125 artists on a scale of 1 to 7; algorithms calculated the compatibility of each of the 1,000 users based on the number of artists they had in common. Users were then e-mailed a list of recommended albums from their highly compatible mates. As its popularity exploded, the increasing number of users made the results smarter. Firefly made Maes a millionaire, and earned her a place on Newsweek's 100 most important people to watch, the World Economic Forum's 100 people to listen to, and People's 50 Most Beautiful People in the world.

Firefly Inc. then went where so many promising startups have gone to die: It was acquired by Microsoft in 1998, and integrated into its less-than-world-changing Passport Web ID product.

The take-home lessons from Firefly—that the intelligence of any user-based system is directly proportional to the number of users, and that you can use math formulas to find art people might actually like—remain the simplest and most frustrating touchstones in the world of recommendation technology. The same concepts are used today to get a sense of what you'll buy on Amazon.com or rent on Netflix. What it's saying is that your tastes are not created in a vacuum, and that there are other people who like what you like. Somewhere is a computer with several gigabytes of music on its hard drive; it has every single album you own—plus two more. Who wouldn't want to know what albums those were?

One of the newest entries into the science of sound selection, iLike, was launched a year ago in Seattle by 34-year-old twin brothers Hadi and Ali Partovi. Ali, who handles the "sales and marketing side of things" from the San Francisco office, is a recreational guitar player who helped found GarageBand.com, a site for promoting unsigned bands. Hadi was most recently with Microsoft. Both brothers hold master's degrees in computer science from Harvard. Their new project melds the online friends-making mechanics of MySpace with the obscure-band infrastructure of GarageBand.

"Our goal is to facilitate social music discovery," says Hadi Partovi.

The iLike offices on Capitol Hill bespeak a typical dot-com startup: Just past the perky receptionist is a tranquil sea of white walls, nubby carpeting, and twentysomething computer engineers whose desks are filled with dual oversize monitors and cans of Mountain Dew. Inside the conference room, a dry-erase board is covered with numbers, grids, and T-shirts bearing the iLike logo.

Also typical is a seeming disregard for profit. This place is so Web 2.0 that even revenue is a distant goal. "We are focused on growing users and usage," says Hadi Partovi. "We will get to revenue as the next step." Right now, the only source of income is "affiliate fees" when users purchase music from iTunes or Amazon through iLike. But somebody has faith in the company's profit-making potential: Ticketmaster invested $13.3 million for a 25 percent share of iLike last September. Not surprisingly, one of the next services on the site will be alerting users to when their favorite bands are touring, and providing links to Ticketmaster.com.