From college campuses to suburban basements, millions of Americans are making a daily habit of an emerging Internet music technology that lets them listen to music without flipping on the radio, then purchase -- or steal -- it without driving to the store. Only seven years old, it's threatening to upset the entire structure of the popular music business.

Called MP3, the technology's continuing spread has many in a state of rising anxiety, worried that it not only will cut out the middleman in the record industry, but the record store and much of the rest of the traditional business structure. Others are excited about it -- for the same reasons.

When rocker Tom Petty posted a single from his new album on the Internet in MP3 format recently, he thought he was creating demand by giving fans a taste of his new music. After only two days, more than 150,000 copies of it had been downloaded, which was the idea. But Petty's label, Warner Bros., apparently nervous about giving away its product, made him yank it from the site.

MP3 has been around since 1992, but as its use has blossomed in the last year, the giants of the industry have worked themselves into a swivet over it, threatening and filing lawsuits in an effort to shut down a booming pirate trade in MP3 music.

But the midgets of the industry -- independent record labels, offbeat artists and more than a few listeners disaffected with the Top 40 -- see MP3 as their opportunity. Listen to the owner of one of the first labels to sell songs in MP3 format: "You put out a record in Des Moines, Iowa, and you upload it on the Internet, and you have the same distribution power as any multinational corporation in the world," said Jeff Price, general manager of New York-based SpinART. "That's un[expletive] believable."

Or consider a listener's perspective: Downloading MP3 files has "introduced me to a great deal of music I would have never really wanted or heard," e-mailed Michael Luttrell, a software developer and part-time musician in Burke. He'll try out an artist by pulling down a pirated MP3 copy of a song -- if he likes it, he'll buy the CD.

Since the phonograph was invented in 1877, recorded music has had to exist somewhere -- at first, on cylinders of tinfoil, then platters of grooved vinyl, loops of magnetic-oxide-coated tape or little plastic-and-metal discs. The MP3 format, however, stores sound in an easily portable digital bundle that can flow across wires, cables and continents. That means music can exist wherever there's an Internet connection -- for instance, Web sites, chat channels, file-transfer sites and newsgroups on which pirated copies of songs and albums are traded. That angers music-industry leaders, who see record labels and artists losing income.

"There's a big difference between music that's given away and music that's stolen," said Hilary Rosen, president of the Recording Industry Association of America. "It's not necessarily the economic harm of today, it's understanding where we're going." The RIAA is leading an effort to develop a copyright-secure format for downloading music.

The industry has issued dire warnings like this before: When dual tape decks first appeared in stores, much anguishing took place over the prospect of people copying music instead of buying it for themselves. Music sales, however, have continued to increase.

MP3 (short for "Moving Picture Experts Group 1, Audio Layer 3") isn't the only Internet-music format. Competitors such as AT&T's a2b and Liquid Music's Liquid Audio have substantial industry backing and claim technical superiority. And Microsoft just released a preview version of its MS Audio 4.0 software.

But MP3 is leading the pack because it's an open standard -- any programmer can write MP3 software. Anyone can be a producer. Anyone can extract, or "rip," songs off an audio CD and turn them into MP3 files. Listeners can use other computer programs and a CD-recorder drive ($200 or less) to "burn" a new audio CD from MP3 files. There are even portable players such as Diamond Multimedia's Rio that let you listen to MP3s away from the computer.

How It Works

In a Georgetown dorm, sophomore Johanna Villegas opened her Web browser to a search engine, typed in a request, clicked on a link and a digital copy of Madonna's "You Must Love Me" flashed across the Internet from a computer in Russia in about a minute. The singer's voice came warbling out of the computer's speakers in CD-quality clarity.

Villegas -- who is also production director for WGTB, the college radio station -- clicked through the internal campus network, looking for other digital-music collections. An array of icons popped up on her screen -- some run by students, to judge from names like "Boneworld" and "Chickenmadness."

Her own collection of MP3 files is a list of 110 songs by artists from Hole to Barry Manilow. Villegas noted one advantage of parking her music on a hard drive: "We had a party, so I took my computer upstairs and plugged it into my stereo," she recalled. "We didn't have to worry about CDs being stolen."

Across town, Bill Rouck, 27, a programmer for the Department of Transportation, started downloading a single by the British band Invincible -- using a regular modem connection.

As the meter on his screen slowly inched rightward, showing how much of the song was already in his machine, he clicked through a confusing list of MP3 files available for download. Then he opened an MP3 copy of a synthesizer-driven instrumental, from a former band of his, and selected a "visualization plug-in" option: As the song played, the screen filled with fluid washes of color, punctuated by vertical waving and writhing lines -- all mathematically generated renderings of the music's pitch and tempo. Instant music video!

Thirteen and a half minutes later, the download finished. A visitor noticed a radio in his office and asked what FM was good for these days. His reply: "News and talk."

To their fans, pirated copies are singles on-demand. Instead of waiting for a radio deejay to play a song, or risking $15 on the album with only a critic's words as a guide, an enterprising, technology-tolerant listener can copy samples, authorized or otherwise, of an artist's work.

One 25-year-old software engineer from Alexandria -- who asked not to be identified because, "Doing the math, I suspect I'm guilty of felony theft, no?" -- described his MP3 habit. "Most of my downloads come from a very small number of private sites," he wrote in an e-mail. "Essentially, it operates like any sort of hobby club -- we excitedly upload the new record we bought, or the out-of-print 30-year-old rarity we pulled off the shelf."

Like many MP3 customers, he downloads music, decides what he likes and goes out to buy that album. "I spend somewhat more now on music than I used to (which was already a lot)," he added. He estimates that he has collected almost 40 gigabytes (some 500 albums' worth) of MP3 songs. "It's a marvelous luxury -- like a radio station I can program at will."

The engineer uses both his taste and his sense of economic justice to decide which music to buy in CD form and which to download for free: "Much of what I actually spend money on is in the indie-rock vein, where I feel like the performer is actually going to receive and value my money. My MP3 downloads tend to be skewed towards the rich or the dead, or people who wouldn't have seen my money anyway, or stuff I couldn't have bought except through record shows or [the online auction site] eBay."

The RIAA's Rosen attacked this as simple opportunism: "It is as much of a theft as walking into Tower and taking the single off the shelf for free, going home and liking it, and saying tomorrow I'm going in to buy the album."

For some artists, MP3 stands not for the loss of royalties, but for liberation from the tentacles of the traditional music distribution system. The biggest headache for non-mainstream musicians is getting their records into stores. The Internet eliminates that headache. "There are so many middlemen between us making our music and the people listening to it," said Rose Marshack, who plays bass for the Poster Children, a band that's been a bit of a you-know-what for the digital-music movement. "It costs us $2 to make a CD, and the people end up paying $15 for it in the store."

In part because it takes so long to download an entire album, Internet delivery of music has created a small online renaissance for singles -- even as the single continues a long decline in stores, from about 24 percent of retail shipments in 1982 to just 8 percent in 1998, according to the RIAA.

San Francisco-based Epitonic, for instance, only "e-tails" singles. President Aaron Newton expressed skepticism about the near-term potential of album downloads. With the modems available today, it takes hours, and most people don't have the patience, he said, even if he might himself: "I remember growing up in rural South Carolina and driving two hours to Columbia so I could buy music. . . . That's a download time."

Whether they sell singles or albums, though, nobody is getting rich from MP3s. Instead, many labels and musicians are using digital-music files as promotional giveaways. The Liquid Audio and a2b formats allow for sneaky marketing tactics: An a2b-released free version of "Take the `A' Train," for instance, stops playing after 30 days of use unless you buy the "Ultimate Ellington" album -- from the Borders.com online store.

Even with the obstacles of slow downloads and buggy software, the future looks bright for this new form of music delivery. Fast connections to the Internet are getting cheaper and more widely available; the research firm Strategis Group predicts that by 2003, more than 10 million households in the United States will be online that way.

So if the idea of a record store is going to change, why not the idea of a record as well? Some in the industry would like to see options besides the canonical 45- to 70-minute CD.

"Artists can release tracks the way they want to," rapper Chuck D of Public Enemy said at the New York Music and Internet Expo this spring. "They could give two tracks away and sell three. And why does an album always have to be 12 tracks? If you want to release a five-cut album, you can do it on the Web."

Another option is selling music via subscription.

"There will be artists who are writing and recording a song a week or a song a month," said the RIAA's Rosen. "They'll want a service where they can get their fans music as soon as they create it."

Michael Robertson, CEO of the MP3.com Web site, wondered whether CDs will even be necessary: "I flew across the continent and took my little two-pound laptop; I have a thousand songs on that."

One problem technology can't solve so easily, however, is the difficulty of finding good music if everybody can put their recordings online. Some see opportunity in this confusion -- for instance, Epitonic pitches itself as a rock critic with a cash register, stocking only music that its staffers would buy on their own.

Others figure that the song will remain the same. "When you had to press your own record and make your own covers and hawk them at shows . . . it at least weeded out" mediocrities, said Jeff Nelson, co-owner of Arlington-based Dischord Records, one of the area's oldest independent labels. "There's still gonna be the same amount of stuff foisted on the public, with the same proportions of good and crap."

Here are some Internet addresses where music can be downloaded.

MP3.com: www.mp3.com

Epitonic: www.epitonic.com

GoodNoise: www.goodnoise.com

Search engine Lycos's MP3 finder: mp3.lycos.com

Liquid Audio: www.liquidaudio.com

AT&T's a2b software: www.a2bmusic.com

Secure Digital Music Initiative, the Recording Industry Association of America's digital-music venture: www.sdmi.org

Staff writer Robert Thomason contributed to this report.

CAPTION: Georgetown sophomore Johanna Villegas's collection of MP3 files contains 110 songs.