Setting and using a "language" property of an audio file in iTunes? I'm a linguaphile, and I have lots of audio files in different languages in iTunes.  I would like the ability to tag a file with the language code, and to see and/or sort by that tag. 

I have no use for Grouping or BPM, so I could use one of those.  But it would be nice to be able to set it in the Get Info window, and to actually see the word "language" in the column headings. 

Is there a way to add a column to the list of available columns? 

Is there a way to add a column not shown, or an ID3 tag not shown, to the Get Info window?

Any search method I can think of is just going to give me a zillion pages about the user-interface language.  If I change the user interface to Canadian English, and add a localization for grouping &rarr; language, will that break anything?
The set of available columns appears to be fixed, and there is no language column.  But the way to change the set of displayed columns is by contextual menu (right-click) on the column headers.  (At least in 12.1—Apple seems to take pleasure in making sure we can't ever get accustomed to any particular UI for iTunes.)

There is a "category" column which I will use.  Not ideal, but better than usurping BPM or grouping.

Update: Changed my mind.  I can put lang: es; in Grouping and search for that in a "smart playlist."  That still allows me to put other things in Grouping.