The dup finder plug-In did not work well
about 4 years ago in MC9 the Option
~Dups And ~NoDups was added
Also Look In The MC Help for Smart Lists For More Information About Smart Lists
~dup=[name],[artist] only keeps files in a list when at least one other file has the same name and artist in the list. You can add as many fields as you like (e.g., duration, album, etc).
~nodup=[name],[artist] only keeps files where no other file in the set has the same set of specified fields..