I've thought some more. Might be useless!
If access.log contains a line like:
[07/Mar/2006:06:24:22 -0800] "GET /mp3/song.mp3 HTTP/1.0" 200 - "-" "Mozilla/5.0 (compatible; Yahoo! Slurp; http://help.yahoo.com/help/us/ysearch/slurp)"
Then a command line like:-
cat pathto/access.log| cut -d'/' -f4 | sort | uniq > tempfile
Should create a unique sorted list of mp3's by name.
The cut command uses -d'/' to mean use a / as a delimiter and -f4 is the fourth field (i.e. counting 4 /'s)so the rest of the command continues from the fourth field and sort sorts the list. If you add the uniq command it removes duplicates. The command list is saved into tempfile.
You might have to jiggle it a bit and change the -f number depending on what your access.log line looks like.