Bringing music to your PC: Our latest tech primer explains today's hottest digital audio format.

MP3 (MPEG-1, Layer 3): a compression standard that creates relatively small digital audio files with high-fidelity sound.

• High-quality digital sound.
• Small file sizes.
• Most widely accepted digital audio standard.
• No system for protecting copyrights.

Why drive to a store to buy music when you could fire up your PC and download the music instead? You say you want a revolution, and the digital music format known as MP3 is primed to lead the charge against audio CDs. MP3 is a compression standard that significantly reduces the size of audio files while maintaining good sound quality.

MP3 files start life in a different format; for Windows users, that format is usually a Microsoft .wav file. Uncompressed .wav files are huge: A file with one minute of CD-quality music is typically about 10MB. Their sheer size makes them difficult to move or store.
That's where MP3 comes in. Compress that same minute of music at 128 kilobits per second using MP3, and it'll occupy about one-tenth the disk space of the original. MP3 encoders create smaller files by getting rid of unnecessary audio information. When you convert .wav files to MP3, an encoder filters out data representing sounds outside the average person's hearing range. Because some of the original audio data is lost, this technique is called lossy compression.

But lossy compression has its downside: The more data the encoder throws out to shrink the file size (a setting you can control), the worse the finished product sounds when you play it back. The result is that not all MP3 files sound alike. For instance, the MP3 industry claims that music encoded at 128 kbps will produce "CD quality" MP3 files--and at that quality, a one-minute audio file fills about 1MB of disk space. But regular MP3 users disagree, saying that they hear significant distortion unless the file has been coded at 160 kbps, which produces files that take up slightly more space but sound much better. MP3s coded at 96 kbps end up as far smaller files but have considerable noise.
Once you have an encoded MP3 file, you need a decoder or player--which can be either software or hardware--to convert encoded MP3 data into something you can listen to. You can download most software MP3 players for free from the Web.