Use media-optical-cd-audio for Audio CD item. If media-optical-cd-audio is not available, use Music emblem.
If media-optical-cd-audio is not available, use Music emblem, on top of (overlay) regular Optical CD icon, just as it is when using emblems in Thunar.
Does Thunar show the media-optical-cd-audio icon or default CD icon + emblem?
No, neither.
What does the terminal command "gvfs-info <mountpoint> | grep standard" return?
$ gvfs-info cdda://sr0/ | grep standard standard::type: 2 standard::display-name: תקליטור שמע standard::icon: folder standard::content-type: inode/directory standard::size: 0 Phrase תקליטור שמע stand for Audio CD in Hebrew.
Can you please also attach the output of "gvfs-mount -li"? The gvfs backend determines which icon should be used and this information is passed to applications like thunar and xfdesktop.
No feedback was provided for a long time, so closing. Feel free to reopen with relevant information if this bug arises again.