OS X 10.8 or later. This applet will assist with swapping, copying, and appending data between two user-chosen tags in selected tracks or tracks in the selected playlist:
Swap - swap data between tags, ex: ARTIST<->COMPOSER
Copy - copy data from one to another tag, ex: ARTIST->
Append - append data from one tag to the end of another, ex: ARTIST->COMPOSER - ARTIST
Prepend - prepend data from one tag to the beginning of another, ex: ARTIST->ARTIST - COMPOSER
The latter three actions also provide an option to delete the info from the first tag after the copy. Read Me explains all.
This update is free for registered users of v4.x.
Select the Action to perform between the two chosen tags in each selected track.
Remove iTunes tracks disassociated from files
Perform search-and-replace on text in your choice of tags
Download selected media from a web page in Safari
Set the Plays of selected tracks.
Gather audio tracks whose files contain no artwork metadata
Two scripts copy text from clipboard to current or single selected track's lyrics tag