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 last known 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.
iTunes can't find the files pointed to by the Location property of these track entries.
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Remove iTunes tracks disassociated from files
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Write size of track's artwork to chosen tag or copy tracks with artwork of certain size to playlist
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Move selected playlists to a new or existing folder
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Batch merge and/or delete playlists
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Exports and then re-imports selected tracks' artwork
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Search Wikipedia using the Song Name, Album, Artist, or Composer of selected or playing track