Dave Greely (L) and Ben Sawyer, co-authors with Justin Frankel on the new book MP3 Power.

BY RAY COOKLIS
The Cincinnati Enquirer

Less than a year ago, the average music fan might have guessed that ''MP3'' was the model number of some snazzy sports coupe.

No longer. Now anyone who's really ''plugged in'' knows that MP3 means music. It's a digital audio format that has exploded in a matter of months from a computer geek's toy into a revolutionary, Internet-based force that threatens to loosen the record industry's decades-old grip on the music business -- and topple traditional broadcast radio stations as well.

MP3 stands for Moving Picture Experts Group, Layer 3. It's a format to compress digital audio files, such as the ones on a music CD, into one-twelfth their original size, with little to no loss of sound quality.

That extreme compression has made it possible for music buffs to quickly post, download and swap music files over the Internet, even with a garden-variety modem connection. Record companies are nervous because MP3, while it has many legitimate, legal applications, can also be used to bootleg commercial CDs and distribute the files freely, without copyright protection.

The two developments that unleashed MP3:

In 1997, a 19-year-old University of Utah dropout, Justin Frankel, developed and freely distributed a program called Winamp that lets even a novice download and play MP3 files on a home computer.

Last fall, Diamond Multimedia overcame a legal challenge from the record industry and released the Rio, a tiny, $199 Walkman-like device that stores an hour or more worth of skip-free digital music. More than 100,000 have been sold so far.

MP3 is hot. How hot? On Lycos, the second-largest search portal on the Internet, ''MP3'' is the second most often searched word after ''sex.''

The Internet is brimming these days with free music files -- legit and bootleg -- for music fans to download.

Some are from start-up bands, like Chicago hip-hop group La Junta, trying to make a name by giving away their songs. Some are from established artists, such as Public Enemy's Chuck D, who are tired of restrictions of big-label contracts.

Now, MP3 is about to become truly mainstream. Mr. Frankel's company, Nullsoft, was purchased June 1 by Internet giant America Online, which couldn't help noticing that Winamp owns 50 percent of the rapidly growing MP3 market.

''Fifty percent of a new medium is worth a lot of money to a lot of people,'' says Andy Shafran, founder of Muska & Lipman, a Hyde Park-based publisher that has just released the first comprehensive how-to book on MP3 with Mr. Frankel as co-author.

''This really validates the MP3 movement,'' says Mr. Shafran, an author of several computer books who predicts that a version of Winamp will be integrated into future versions of AOL's online software.

That mainstreaming may mean that MP3's pirate days are already winding down, as the music empire strikes back by developing copy-protection standards for digital formats. And Mr. Frankel has said that Winamp will begin to incorporate some form of copy protection.

But another traditional entertainment medium may be in MP3's sights: radio. A new software package developed by Mr. Frankel, called SHOUTcast, allows literally anyone with a computer to operate an MP3-based radio station over the Internet -- and anyone else with a computer to ''tune in'' live to their choice of stations.

''The radio is moving to the Internet,'' Mr. Shafran says.

As they say, blame it on Rio.

The players