OS X 10.8 or later. Copies your single choice of filename, file path (location), file's parent folder path, file creation date (YYYY-MM-DD HH:MM:SS), current playlist, volume adjustment, start time or stop time (HH:MM.SS), artwork size (WxH), purchaser name or purchaser account ID to choice of Category, Comments, Description or Episode ID tag of each selected track. By putting data in one of these available tags it can be visible and sortable or used with Smart Playlist criteria.
I've kept the word "Comments" in the title of this script for legacy purposes, even though modern versions of it can write to other tags.
Choose the information to use (left) and then choose the tag to copy it to.
(via in-app purchase)
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