OS X 10.8 or later. This script will look for an image file in the parent folder of each selected track's file--presumably its Album folder in which you have previously placed an image file of some sort--and apply the data from that image file as artwork for the track.
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View/Edit tags of selected track(s) in single window
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Convert selected tracks and export the converted files to a new folder
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Locates pairs of track entries pointing to the same file
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Add or subtract a user-entered number from each selected track's Plays