ACRCloud - Automatic Content Recognition (ACR) cloud services for Audio Recognition ( identify music, ads ), Broadcast Monitoring, Second Screen, Copyright Protection.
Idupe - iTunes has a “Show Duplicates” command, but it is of limited use.
AudioTag - AudioTag.info — is a free music-recognition service.
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.
AHA Music - AHA Music is a music identifier on Chrome, it detects songs playing on your browser with Spotify...
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.