Thanks very much for clearing that up for me!
Looks like I'll have to get them then. I think the CDs are just a digitized and re-released version of the cassettes, so they're probably just the same.
You wouldn't by any chance happen to know where I can get the audio for "KALAALLISUT SUNGIUSAATIT", would you? Apparently the audio cassettes for that book are really good as well.