BLACKSBURG -- Lilith Fair founder Sarah McLachlan and pop star-turned-tabloid-target Britney Spears have different fan bases. But their music can sound similar, according to the creator of a popular online radio site that groups songs based on more than 400 components of music.

Exposing listeners to songs they are likely to enjoy but unlikely to have encountered is one goal of Pandora Media Inc., said founder Tim Westergren, who described his company and its plans for the future to nearly 100 people Tuesday night at Virginia Tech.

Launched eight months ago, pandora.com has grown to about 3.3 million registered users, who type in the name of an artist they like and are then provided free, streaming audio of songs similar to the chosen artist's music.

Westergren said he is traveling the country to get feedback from users of the site to make it better. He chose Blacksburg in part because about 1,800 Tech students have registered at his site, second only to the University of Michigan among colleges.

Pandora grew out of an initiative called the Music Genome Project that began in 2000, when a group of trained musicians started listening to songs and classifying them based on sound elements.

Six years later, Pandora employs 42 expert listeners and has classified more than 500,000 songs. It adds about 15,000 new tunes each month, Westergren said. It takes about a half-hour to classify each song. The company gets about 30,000 song submissions a month, but its employees also search for music on their own. About one-third of what is listened to winds up being entered into the "genome" and streamed, Westergren said.

Pandora plays songs that meet its quality standards whether they are by major acts or unknowns, and the site has become an outlet for new bands trying to develop an audience. Two-thirds of Pandora's catalog is not on a record label, Westergren said.

Audience member Kelly Bernd, 21, said she tried the site Monday and was impressed that it not only had music by a relatively obscure Australian artist, Xavier Rudd, whom she had seen at a festival, but songs similar to his that she also enjoyed. "I thought it was great," she said.

It is now common for companies to use data to predict consumer tastes and pitch products to them. Netflix recommends movies to its subscribers based on their reviews of past rentals. Westergren said he used to license his technology to Amazon.com and others to use for purchase recommendations. But his business strategy has shifted to selling ads on a high-traffic online radio site.

Pandora's goals in the near term, Westergren said, are to make its site more interactive, to enable people to access it though cellphones or MP3 players, and to set up an international service. Because of rights issues, pandora.com is not a legal site outside the United States, but it is believed that many people abroad use the service.

Pandora asks its users to enter a ZIP code to access the site. The most common one, Westergren said, is 90210. The Beverly Hills code is famous from a television show.

On the Net: www.pandora.com