To copy an audio CD is more involved, mainly because
it's impossible to
guarantee that you get exactly the right "sectors" in exactly the right
order from the original (a consequence of the way frames are labelled in
CD-DA format). Tools like cdparanoia solve that by reading overlapping
sections, and doing a lot of sliding comparisons to build up an accurate
copy (it creates a WAV file for every track). That's why simpler methods
often produce copies that don't sound exactly the same, though some CD-ROM
readers do a pretty good job at getting a clean audio stream, especially in
conjuction with software like readcdda or cdda2wav.
I've only used it a few times, but "cdparanoia" is a damn good tool for
what it does. Excellent at reporting error correction levels necessary for
reading the audio CD, too.
Tim.