It's rather odd that Disk Utility is confirming the operation as successful, yet the images can't be read by your system.
There could be a number of reasons for this, including an issue with the CD itself, the disk drive, or the Disk Utility software. The other potential issue is with Digital Rights that can be associated with a music CD.
As a first step, try creating a disk image from a different non-music CD to rule out a problem with the CD itself. If the problem persists, we can try to reset Disk Utility's settings.
To reset Disk Utility, follow these steps:
1. Quit Disk Utility if it's open.
2. Open Finder, go to 'Go' in the menu bar, hold down the 'Option' key, and select 'Library'.
3. In the Library folder, open the 'Preferences' folder.
4. Locate the file 'com.apple.DiskUtility.plist' and move it to the trash.
5. Restart your Mac and try creating the disk image again.
Keep in mind that deleting this .plist file will reset all Disk Utility settings to default, so make sure you're okay with this before proceeding.
If the issue still persists, you might need to repair your disk permissions, especially if you recently updated your system.
Here's a link to Apple's support article on how to repair disk permissions:
Also, here's another support article that might help: