Internet radio and services that deliver personalized streams of music -- and help you discover new music and artists --are growing exponentially. In fact, they seem to be becoming a viable medium for promoting recorded music -- possibly replacing the shrinking broadcast radio audience. That makes it pretty ironic that the recording industry's aggressive push for performance royalties could kill Internet radio just as it shows some promise of throwing the record companies a life ring.

What's happening is that Internet radio is entering a new phase of its development. At first it was generalized, as broadcast radio stations streamed their over-the-air signals online as a promotional device. Then it became specialized, as Internet-only "stations" were created to serve niche markets. Now it is being personalized and, inevitably, socialized.

		6 Internet Radio Services
		•  Introduction •  Pandora •  Last.fm •  Slacker •  TagWorld •  Live365.com •  LAUNCHcast
		•  A Dangerous Ruling

Personalization lets listeners tell a site to "play music like this" by seeding their channel with a few favorite artists, tracks, or albums; the site then matches the user to more music. The simple way is to funnel the user into a playlist. But more and more, advanced sites are beginning apply algorithms that pick tracks based on the user's real-time feedback. On the cutting edge of this method are sites like Pandora, Last.fm, and Slacker.

Socialization is, of course, the melding of social networking with music sites. New music sites aren't immune, after all, from the pressure to be the next MySpace. Done well, the combination can introduce a new dimension to the search for new music and artists by letting you rate or tag tracks, share playlists, and listen on other people's channels. Done poorly, it can feel like a time-wasting invasion of privacy. Yahoo's LAUNCHcast selections are ratings-based, while Last.fm and Tagworld encourage you to add descriptive tags to tracks.

In this roundup, I look at six current Internet radio sites in terms of how well they deliver music you want to hear, and how well they help you find new music to add to your personal playlists: Pandora, Last.fm, Slacker, TagWorld, Live365.com, and LAUNCHcast. (Note: Since this roundup was written, I've come across several other noteworthy services, which I cover in a follow-up blog entry.)

Most of these sites give you a "love it/hate it" option -- click "love it" and favorite tracks show up more often, "hate it" and banned tracks are supposedly gone forever. But all of the sites get more sophisticated than this, and each does it a little differently.

A note for those who dislike ads: While most of these services are drenched in advertising, generally I didn't find it offensive, Why? Because it's appropriate: If you hear something you really, really like, you just might want to buy it. Paradoxically, though, this formula of listen-and-buy -- the same formula that has helped broadcast radio and the record companies prosper together for decades, -- could be a potential casualty of the recent rate-setting pronouncements by the Copyright Royalty Board, which imposed massive increases in performance fees on Internet radio stations (but not against broadcast radio) as a result of music-industry lobbying. (See sidebar.)