[ale] Unclear on mixed-mode CD-Rs (or whatever they're called)

[hbbs at comcast.net (Jeff Hubbs)]

I'm trying to produce a CD-R where if you put it into an audio CD player
it plays audio tracks and if you put it in a PC, Mac, etc. you see some
files you can copy off (.pdfs, etc.).

I've tried doing this in k3B and by hand with cdrdao (following various
online resources) and all seems fine except for the data business - a PC
can't see any files there.

Any URLs or pointers?

Jeff