Idupe - iTunes has a “Show Duplicates” command, but it is of limited use.
Shazam - Shazam is a mobile app that recognizes music and TV around you.
Tune Sweeper - Show duplicates in your Music library. Automatically select which duplicates to keep and delete based on your preferences. Remove duplicates with one-click from your iTunes or Music app library.
SoundHound - SoundHound - the most immersive music search, discovery and play experience on mobile.
Leawo Tunes Cleaner - Leawo Tunes Cleaner is a powerful iTunes cleanup tool, which can help you to delete duplicates in iTunes and get album artwork for iTunes music files.With it,you can clean up iTunes music library fast and comprehensively.
Midomi - midomi.com find and discover music and people.