@Frank:
The good news is: I found that field indeed... under podcasts (as you say). (More good news: always glad to find out new things merely by following the forum :-D )
The bad news: I'm afraid it's not available for Library Music...
Thanks for posting the screenshot. Of course, yes.
(I couldn't find it, coz I had something else in mind (what doesn't make sense after all...) never mind... ;-) )
@7amza: guess you'll have to post this as a wishlist item...
(field setting for %Track and/or %Album)
b.