Maybe you heard this:
when burning data on for example a 74min cd, you can put about 650MB on the cd. However, when burning audio, while the wav files can take 600-700MB on your HD, it will still fit on the cd. This is because of somekind of compression. I'm not sure exactly how it works, but that could have been what you have heard.
Of course it is also possible to create a MP3 cd, which can contain up to 12 hours of music. But then the cd would only be playable in CDROM's DVD players and MP3 cd players.
[Edited by djewst on 16-03-2001 at 20:41]