I found this thread to be the most helpful but I have never done what
you are attempting. It seems to be fairly complex and controversial!
Do you really need to send the audio to the duplicating firm in .iso
format? Seems to me GIGO applies here - if you send an .iso it will be
duped as an .iso, not as playable music. But maybe I'm just totally
confused...

www.linuxquestions.org/.../creating-an-iso-from-an-aud\
io-cd-with-dd-670913/