Hello,
I've searched across the iTunes API and retested a few exemples of my library, but it doesn't look like iTunes has the "Composer" field available for processing. Can you provide an album page that has a Composer value (as in the url of the iTunes page, like _https://music.apple.com/jp/album/383274167?l=en)?
Or can you give some more details of what would you like to have my script do?