OS X 10.8 or later. Append the same user-entered text to the beginning or ending of the existing text in the chosen tag (Song Name, Artist, Album Artist, Album, Composer, Comments, Genre, Grouping or Show Name, and their Sort siblings) in each selected track.
For tags other than "Song Name" and "Show Name", this script may be just slightly less involved than performing a multi-edit on the selected tracks.
Also see This Tag, That Tag.
Preview each track as it will appear after applying the entered text.
Displays files in iTunes Media folder not in iTunes track library
Remove iTunes tracks disassociated from files
Copy Artist to Album Artist of selected tracks
Exports and then re-imports selected tracks' artwork
Export selected tracks' data to XML file, import later
Locates pairs of track entries pointing to the same file