There's an upside and a downside to being a music-loving baby boomer. The upside is that you had a chance to see Jimi Hendrix, the Doors and maybe even some of the original Motown groups. The downside is that every day you're getting closer to meeting Jimi Hendrix. Before that happens, though, why not hear some new sounds to augment those Beatles, Dylan and Talking Heads tunes you've played a billion times? It turns out there's a way to identify new artists to add to the vast digital expanse of your iPod--ones that fit your personal sweet spot--without schlepping around in the desert heat of the Coachella Festival. Just do what you do when you want to find anything these days: go to the Web. The advent of digital music (with the help of a new tech boom) has led to an explosion of start-ups whose goal is to direct users to artists and songs that satisfy their individual tastes. These turn out to be perfect for rockers of a certain age who crave the energy and innovation of new bands, but don't want to stray too far from the music they've always enjoyed.

One of the early discovery sites is Pandora, founded by former musician Tim Westergren. While working as a film composer, Westergren found that directors often had difficulty describing the sort of sound they wanted. He learned it was best to have them pick a few songs they knew that fit their criteria; then he would create something like them. That got him thinking about what could happen if you understood what he called "the DNA of music." "It would be a really effective way of connecting people with music they liked," he says, "based on something they already know."

So Westergren spent years charting the musical equivalent of the genome--the set of characteristics that expresses the song's ultimate sonic form. These musical genomics are the secret sauce in Pandora, an individualized set of instant Internet radio stations. Every time a song arrives in Pandora's musical DNA shop, one of its 40 music analysts will devote 20 to 30 minutes of intense concentration to identifying as many as 400 distinct variables, or "genes." Just in capturing the emotional metrics of the singing voice, there are 32 variables--such things as timbre, vibrato, pitch and range. When this system is applied to all the instruments, as well as the overall traits of the song--tempo, amplitude, etc.--the analyst produces a précis that captures the song's essence.

Pandora works by asking you to pick your favorite artists and then programs a radio station for you. You can tweak the selections by giving thumbs up or down to a tune (when a Ratt song stuck its snout into a session, I exterminated it quickly) or by adding a new artist to the mix. One of the songs may well introduce you to a great band you never heard of--or it may expose the fact that you have a recessive musical gene for something completely unexpected. Westergren sometimes gets searing missives from rock snobs who are outraged that Pandora had concluded they might like Céline Dion. ("It's a social objection," he says. "So what if she's doing Las Vegas--she can sing !") The ad-supported site went public last November, and Westergren says he has more than 2 million users.

Some newer sites take a different approach, in keeping with the recent Web trend that puts users at the center of activity. "We are trying to do something with the wisdom of crowds," says Martin Stiksel, cofounder of a U.K.-based service called Like Pandora, offers personalized radio stations, but instead of using experts to determine similarity, it gauges your own tastes (by using a separate application, Audioscrobbler, to log and analyze the songs you play in your own computer library and even your iPod) and then draws on the collections of its users for ideas. The theory is that you'll like the songs favored by people whose playlists overlap with yours.

That technique, known as collaborative filtering, is also the basic idea of a Corvallis, Ore.-based start-up called MyStrands, which asks users as well to download a small application that tracks what they listen to in iTunes. Every time you play a song on your computer, MyStrands instantly digs into its "matrix of associated songs" and suggests a few other tunes that may not be in your library, or even on your musical radar screen. These aren't chosen strictly on the basis of similarity but, says My-Strands VP Gabriel Aldamiz-echevarria, "from the fact that a thousand people may have liked to hear those songs together." That explains why songs evoked by Janis Joplin's "Get It While You Can" aren't necessarily by gutsy wom-en blues belters, but can include the Canadian punk band Hostage Life. Encountering a collection rich in Dylan, John Prine and Doug Sahm, MyStrands craftily points to the underappreciated Austin-scene singer-songwriter John Dee Graham.

Instead of an algorithmic method of tapping the wisdom of crowds, MOG, a start-up that began its public beta just last month, uses a social-network model. When you first set up your profile on the site, an application called the MOG-o-Matic sucks up all the titles in your library (not the music itself) and posts it for all to see. (You can edit out embarrassing lapses.) Your tastes become a calling card for others in the community--and you can ask MOG whose playlists might be similar to yours. "It analyzes your collection to help you find people like you," says CEO David Hyman. MOG hits a relatively young demographic, but it's a great place for a boomer to get musical suggestions from twentysomethings without coming on like a stalker. And since the site is geared to lubricate interaction among community members with forums, blogs and e-mail notifications, it's not uncommon for obscure artists to become chartbusters in the MOG world. You may not have heard of Band of Horses, but if your collection is loaded with Gram Parsons, R.E.M. and the like, you'll keep bumping into MOGs who love them. As it turns out, a Pandora radio station based on Neil Young also lit on the Seattle-based band.

Pandora,, MyStrands and MOG are only a few of the dozens of sites and services springing up to mine the explosion of new music that's coming in the age of Internet distribution. And established services like Apple's iTunes, Amazon and Microsoft also have their own recommendation strategies. "This is really a great moment, a wonderful time to learn about music," says MyStrands' Aldamiz-echevarria. Boomers who want to expand their horizons would do well to take advice from dear departed Janis: get it while you can.