When the Recording Industry Association of America (the RIAA) sued Diamond Multimedia last November to prevent the company from shipping the Diamond Rio PMP300 Portable Music Player, it let a very big cat out of an even bigger bag. The world suddenly realized the Net is the largest music store in the universe, open 24 hours a day 7 days a week, with more tunes than any ten stores could stock. There are no smirking counter clerks with multiple pierced body parts, either.

Although you can purchase retail CDs over the Internet, the most significant benefits extend beyond this simple convenience. Technologies such as RealAudio have familiarized us with the concept of listening to audio broadcasts--concerts, simulcast press conferences, or music tracks--in real time (called streaming audio) on our PCs. The technologies explored here give you the opportunity to download music files to your hard disk or burn them onto CD-ROMs.

When it comes to contemporary music, you can sample before you buy, you can usually buy one or two songs instead of an entire album, and with the proper hardware, you can create CDs that play on your car and home stereo systems.

The Technology Story

To get started, you'll need an MP3 player or software that can play MP3-compressed audio files. That's because most Internet music is compressed to enable faster distribution and require less local storage. MP3, or MPEG Audio Level 3, is the audio side of the MPEG video specification, which offers near-CD-quality sound at very high compression ratios.

A public standard, MP3 has emerged as the Internet's most popular compression format. Microsoft Windows 98 includes an integrated MP3 player, as does the new Microsoft Windows Media Player; you can also download a free MP3 player at a number of sites, including www.mp3.com. All players let you listen to MP3 files, and some also convert them to WAV files that can be burned onto CD-ROM, a process described below.

Though many sites sell or otherwise distribute legitimate MP3 files, a growing number make available unauthorized files, violating the copyrights of record labels and artists. In the record industry's eyes, this makes MP3 a fox in the digital hen house, eating chickens and eroding profits.

In fact, the popularity of the MP3 format was the real motivation behind the RIAA's suit to enjoin Diamond's shipment of the Rio, the industry's first portable MP3 player. Diamond ultimately won and the Rio shipped, though the RIAA appealed the decision.

Whether successful or not, the RIAA lawsuit won't immediately affect the distribution of legitimate MP3 files over the Internet. This makes knowing how to work with MP3 files invaluable for those seeking to mine music on the Web.

Simple as A2B

An MP3 player is not the only musical decoder ring you'll need, however. The record industry's concern over MP3 has spawned several technologies that provide similar compression schemes--plus copyright protection. Most notable are Liquid Audio (www.liquidaudio.com), and AT&T's a2b Music (www.a2bmusic.com).

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These technologies provide significant distribution flexibility, which in turn encourages record companies to release additional music for online listening or download. Both can limit playback of the audio file to the computer that originally downloaded it and can time-out playback after a certain number of days.

These technologies also appear in players that provide liner notes, lyrics, and album graphics, enhancing the listening experience. Though only Liquid Audio offers the ability to burn downloaded tracks to CD-ROM, AT&T plans to introduce this capability soon.

Finally, RealAudio (www.real.com) may also play a role in your music hunt, primarily at sites featuring MP3 files. Most MP3 files contain 128K of data per second of music, which translates into long wait times to sample the music. For this reason, many MP3 sites also offer instant streaming previews via RealAudio, as do several Liquid Audio sites.

Now in Aisle Three

Though you can buy retail CDs online, the Internet offers a much wider selection and a range of business models. Some sites, such as GoodNoise (www.goodnoise.com), function like boutique record labels, signing a small number of bands and distributing their albums. You can sample 30-second clips from all songs in MP3 and RealAudio format and even download a free MP3 song or two, but you can't buy a CD-ROM online. Instead, you buy and download all your selections, usually at $0.99 per song and $8.99 per album.

By contrast, MP3.com (www.mp3.com) represents nearly 2,000 artists--some no-name, some well known. Every band selects one song from each of its albums for free distribution, so you can download a diverse collection of music without paying a cent. To get a complete album by a single artist, though, you have to buy the physical CD (usually for under $10).

Amplified.com (www.amplified.com) pursues a straight distribution model, offering a diverse range of artists such as Richie Valens, Frank Sinatra, and Billie Holiday using Liquid Audio and including RealAudio previews. Songs typically cost $0.99, and you can purchase only via download.

If your goal is to download individual songs, don't set your sites on popular albums from mainstream artists: Most record companies don't release best-sellers for download distribution to avoid conflicting with store-based distribution. On the other hand, if you're looking for hard-to-find songs unavailable in record stores, boot up your computer, fire up the modem, and crank up those speakers: You're probably in the right place.

Here's a look at how to get what's out there.

— Jan Ozer