Before any of that can happen, however, more people need to understand the practical ins and outs of the digital music phenomenon. Here, then, is a primer.

What is this MP3 thing?

It's a computer file format that compresses the digital files containing the songs to a tenth of their normal size, without any sacrifice in audio quality that can be detected by a normal listener. A typical five-minute song might occupy 50 megabytes of space on a CD, which is itself a digital storage medium. But the MP3 version of that same song would be just 5MB, small enough to download in a reasonable time, even with a dial-up modem.

Is MP3 the only popular format?

Yes, for now, but others are on the way. Microsoft has introduced a format called WMA, which in some cases offers quality equal to MP3 with even smaller file sizes. The record industry is working on yet another format that can handle security features MP3 can't -- such as digital payment schemes or barriers to copying files.

Is it legal to download and play these MP3 files?

In most cases, it is legal. There are some bootleg MP3 versions of famous albums on some Web sites. But these illegal download sites are vastly outnumbered by perfectly legal sites that offer songs, mainly from unknown bands, whose owners want you to download them.

Where can I find these legal downloads?

Try www.mp3.com or www.emusic.com, for starters.

Is there any way to get MP3 versions of songs by name artists?

Yes. A few well-known artists have begun offering some of their music online in MP3 format. Also, you can legally convert tracks on CDs you own into MP3 files on your hard disk. To do that, you need a program called a "recorder," or "ripper," available free on the Web.

Why would you want to do that if you already own the CD?

To create your own song collections.

Are there any other advantages to MP3 files over standard CD tracks?

Yes. MP3 files can contain data about each song, such as artist, album, genre, notes, lyrics and even an embedded photo of the artist or album cover. This nonmusical data is called a "tag."

How do you play these MP3 files once you get them onto your hard disk?

You'll need a program called a "jukebox." These do much more than merely play your MP3 songs. They collect them all into a library, let you edit the song tags and group any combination of songs you want into automated playlists, which are like virtual CDs. Some of the programs also include a recorder or ripper.

What are some of the names of these programs, where do you get them, and what do they cost?

My favorite is MusicMatch Jukebox, available at www.musicmatch.com. It's the only one that can display lyrics and photos while a song is playing. Another good one is Winamp, at www.winamp. com. Others include Sonique, at www. sonique.com, and RealJukebox, at www. realjukebox.com. Most are free, though some charge for extra features.

How can I listen to these MP3 songs when I'm away from my PC?

Two ways. If your PC is equipped with a CD recorder, or "burner," you can use special software to copy music onto blank CDs in the proper format. When you're done, you'll have CDs that can be played in almost any CD player. Or you can download songs from your PC into one of the new portable MP3 players.

What's a portable MP3 player?

It's a palm-size gizmo with a chip and solid-state storage that can retain and play MP3 files. There are several on the market, including the RioPort Rio, the Creative Nomad and the RaveMP by Sensory Science. More are planned. You connect the player to the PC via a cable, download the music files to the player and take off.

Can I play MP3s on my home stereo?

A couple of companies have announced plans to sell home stereo decks that play MP3s. One will actually contain its own internal hard disk and will connect directly to the Internet. The other will play CDs filled with MP3 files rather than the normal audio format used on CDs.

(www.ptech.wsj.com)