Hi tyndareus, welcome to the forums.
You cannot save an audio CD (or a single track of an audio CD) to an ISO image. This is because an audio CD does not include a filesystem, so ISO images can be used only for DATA (using the ISO9660 filesystem and eventually some extensions).
Audio CD can be saved as a CUE/WAV couple of files, or with a proprietary format (.NRG for Nero, .PXI for PlexTools, etc.), while audio tracks can be saved in .WAV format (or in a compressed format like APE, FLAC, MP3, OGG, ...)
Also, please note that the post you answered is dated 14-03-2004, so probably RaysMD has already found the answer he was looking for.