That's where Joseph Patel, an MTV News producer and regular reader of the blog, heard the song. He also loved it, and decided to put the Hysterics on the air, despite the fact that they had done little more than practice in drummer Geoff Turbeville's parents' bedroom. After the segment was broadcast on MTV, Music for Robots (www.music.for-robots.com) found itself with a new audience: teenage girls, who had come to declare their love for the Hysterics. The band is now in talks with a major label.

And now Mr. Connolly and his Music for Robots peers are attempting a coup of their own. The blog recently released a compilation CD, Music for Robots Vol. 1, which features 19 unsigned and independent-label bands, including the Hysterics. The release represents a break from the way most music blogs operate; typically, blogs of this genre feature enthusiastic testimonials about bands and free downloads of the bands' songs, but no songs for sale.

"The fan base we've managed to build up - a lot of them know that what we're trying to get them to buy is something good," says Blair Carswell, one of the Music for Robots contributors.

The blog started out simply as a way for eight friends, most of whom met at Bates College in Lewiston, Me., to tell each other about music they liked. As readership increased, more bands started sending the group music to post on the site.

"It's this great way for bands who aren't going to get on the radio to get exposure," says Mr. Carswell.

Only a handful of music blogs, with names like Fluxblog, Stereogum and Largehearted Boy, have any influence, but even those still have a long way to go to fundamentally alter the landscape of the music industry. Many labels view blogs as little more than potential providers of free publicity; even a blog like Music for Robots, which gets about 8,000 unique visitors a day, is little more than a blip on the radar of major labels.

But blogs are acting as incubators for new talent like the Hysterics. It's doubtful that MTV would have discovered the band as quickly otherwise.

"It sounded like really moody, old-school pop music - the kind of thing that a lot of bands aim for but never get quite right," said Mr. Patel about the Hysterics. "You don't see that from many adult bands, let alone teenagers in Brooklyn."

Many bloggers who post songs can find themselves in ambiguous legal territory, even when they have the permission of bands or labels. And some more-established bands have not embraced blogs, in the fear that they will hurt sales. The Decemberists, a popular independent band from Portland, Ore., recently complained that much of its new album had been posted on blogs before the album was released, and implored bloggers to take the songs down.

One difference between peer-to-peer networks and blogs is that while the former depends on anonymity, the latter fosters a sense of community. Most bloggers exhort readers to buy the CD's of bands they like, and their enthusiastic posts can bring prominence to bands that otherwise might not get much attention.

"Music for Robots has the credibility of a very hip record store," says Glenn Peoples, who runs a popular music blog called Coolfer. Good music blogs, he said, let consumers get the word out about bands that are legitimately good.

As a business venture, the compilation CD is not a threat to the music business yet. Music for Robots created 1,000 CD's, but only around 150 have sold in the two weeks they have been available. Because music fans have come to expect to hear bloggers' favorite bands free, the people behind Music for Robots know they're taking a risk by charging $10 for an actual CD.

For labels, blogs can be fertile testing grounds. Adam Shore, label manager at Vice Records, said he fell in love with the Norwegian pop star Annie, who was at the time unknown in the United States, but was skittish about putting out her album until he saw the positive word of mouth it was receiving on blogs, as well as on the online music magazine Pitchfork.

"Then I knew it wasn't just me - that there was this whole community of people who feel the way I do," says Mr. Shore. "It made me feel more comfortable moving forward. Blogs are this amazing resource for us."

But the most significant force to emerge for unknown bands, in fact, has nothing to do with the Internet. Starbucks, the coffee retailer, has begun selling CD's in its stores, and the experiment has proved a success. The company recently plucked a band called Antigone Rising from relative obscurity, cutting a deal to sell its latest CD exclusively in Starbucks stores. The CD has sold more than 35,000 copies since it was released on May 11, according to a Starbucks spokeswoman.

For many blog readers, however, CD's are old news. "One usually checks music blogs in order to avoid contact with physical objects like CD's and the corporate machinery they imply," says Hua Hsu, a Harvard graduate student who writes about music for the online magazine Slate. Still, he says he thinks there is reason to embrace Music for Robots' efforts.

"If everyone else is putting out horrible CD's," he said, "why not buy something from people with taste you more or less trust?"