I provided a suggestion to your original post to try out.
Did you try it?
Did it work?
I have a similar question for choral music library. I am trying to calatogue sheet music. Some documents contain a single song RE: "Row Your Boat". Others have a collection title RE: "Rowing Songs" and include multiple songs RE: "Row Your Boat", "Oar or Paddle", and "A Stern Port". How can I track these so that I can look at the song level, but still see the title of the colletion.