OS X 10.8 and later only. This applet checks your entire iTunes library for missing and presumed dead tracks--those tracks that iTunes is unable to associate with a file and which are listed in iTunes with a "!"--and can create a text file listing these tracks by alleged File Path (if available), Song Name, Artist and Album, which you can view using TextEdit.
Also see Music Folder Files Not Added
To find and delete dead tracks see Super Remove Dead Tracks.
See the video on YouTube.
iTunes can't find the files pointed to by the Location property of these track entries.
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downloaded 1s ago
Locates pairs of track entries pointing to the same file
downloaded 10s ago
Remove iTunes tracks disassociated from files
downloaded 1m 9s ago
Enter text for the selected tracks' Category tag
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Copy Artist to Album Artist of selected tracks
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Duplicate tracks from all levels of a selected Playlist Folder to a new playlist
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Enter text for the selected tracks' Description tag