MC 20.0.122 running on OSX 10.6.8:
Inserting an audio CD into the CDROM drive causes MC's Drives & Devices to display an item labeled "Compact Disc (/dev/rdisk4)" in its drop down, but when that item is selected, the tab at the top reads "No disc in drive", and below that, a "Refresh" button is displayed above the text "Insert a disc and refresh".
Where the disc data should be displayed is the message (in very large type):
There is no disc.
Insert a disc and double-click here to refresh.
Double-clicking does not help MC find the audio CD.
The inserted disc does appear at /dev/rdisk4 and its tracks do all show up in /dev/rdisk4*.
When the audio CD is ejected (via Finder), the "Compact Disc (/dev/rdisk4)" item disappears from MC's Drives & Devices. (However, the tab at the top still reads "No disc in drive", and below that, the "Refresh" button as well as the "Insert a disc and refresh" text is still displayed.)
I have tested this failure with two audio CDs (so far). I have subsequently successfully dubbed those two CDs in iTunes, and in the past I've played them on various CD/DVD/BluRay players and they are fine.