Your selection contains more then one kind of media all items must be of the same kind in order to view or edit them togetherThis was not a problem before the recent update.What is wrong.

Why is this happening now. I select multiple Voice Memos and try to edit and it gives me the "your selection contains more than one kind of media" error. WHY?

So, I just ran across this irritating problem having finally updated iTunes. Very, very annoying. I don't really understand because all the files I selected were mpeg audio files, how are those different? In any case, aside from the script mentioned in previous replies, I also found this dead simple way to get the old "Get Info" window/options back and it works as it did before. Select multiple items, edit, save. Done.

"The Annoying Info Window"

As you investigate this new window, you’ll find that some of the tags are no longer accessible, and you’ll also note that the tags are contextual; they depend on the type of media file you’ve selected.

If you’re familiar with the older window, and would prefer using it, you can still do so. Just select one or more files, press the Option key, right-click on the selected file(s), and choose Get Info. You’ll see a window almost exactly like that of iTunes 11 and earlier.

Source: http://www.intego.com/mac-security-blog/how-to-fix-itunes-12-biggest-annoyances/

Thank you Doug!

iTunes upgraded itself yesterday to 12.1.2.27 and now the right-click Get Info doesn't work any longer for a mix of files, and I'm getting this error. I use it to easily shuffle my podcasts (by selecting several files including some that are music, clicking Get Info and unchecking "Skip when shuffling"). Would love to hear if you still have a work-around for your use case with the new version. So frustrated with Apple.