iTunes 12 has made a mess of tagging media files; the new Info windows are hard to navigate, and, depending on the type of content you’re editing, the tags you see change.
Doug Adams, purveyor of the wonderful Doug’s AppleScripts for iTunes came up with an AppleScript-based applet that lets you edit all the tags in a single window. Using this, you not only can avoid the hard-to-manage iTunes 12 Info window, but also not have to switch tabs to edit multiple tags.
The $2 Multi-Item Edit gives you a single window where you can edit most of iTunes’ tags. (Album Artwork is one that’s not available.)
Check out Multi-Item Edit. It’ll definitely save you time tagging your iTunes library.