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I have had some luck recovering data from burned discs using the command-line tool ddrescue:
https://www.gnu.org/software/ddrescue/ddrescue.html

A version for Mac (OS X 10.5+) is available here:
http://tinyapps.org/blog/mac/200808220700_ddrescue_for_leopard.html

ddrescue doesn't itself do any error correction, but rather extracts the readable data bit by bit -- 
often at many times slower than real-time, depending on the number of errors -- to a disc image 
file representing a complete read of the disc minus any bits that are missing.  You can then mount 
this disc image (OS X will do this natively) as if it were a CD-R and use the CD ripper/audio 
extractor/error correction software of your choice on it, which may be more successful than on-
the-fly correction from the optical disc itself.

Another feature of ddrescue is that you can run it multiple times on the same disc, and each time it 
will go back and try to fill in the bits that are missing.  That obviously won't work with data that's 
completely gone, but sometimes can recover data that didn't read correctly for some other reason.  
And these subsequent reads are faster because the program is only addressing the missing data, 
and skipping over the parts it has already successfully captured.

But the best case will be if you have two copies of the degraded disc.  In this case ddrescue can 
scan both copies, merging them into one image that will probably be error-free, since it's unlikely 
both discs have degraded in exactly the same places.  And again, only the missing bits are read 
from the second disc in an attempt to fill in the gaps.  [Disclaimer: I haven't used this particular 
feature of ddrescue myself yet, but am describing it based on information on the project's web 
page.]

It's a bit more involved than popping a disc in, firing up iTunes and clicking "extract," but it's 
worked for me when nothing else would.

- Aaron

--
Aaron M. Bittel
Archivist-Librarian/Digital Projects
UCLA Ethnomusicology Archive