For this release the detailed tracklist groups tracks in a variety of non-work based ways.
Neither Style/Titles nor Style/Classical/Track/Title shine light on the way forward when I read them.
How do I go about including these groupings in the tracklist?
(I’m inclined to treat this as a classical music release - even though penguin suits don’t feature. 
)
In one word: tracksets (feature ticket). 
You can add a tag like mine to your releases for later edit if/when it is available.
Have added suggested tag and an annotation.
The absence of the trackset would be a serious flaw in the metadata for this release group.
Thanks for your help jesus2099.
(Having been raised a Christian it gives me a special thrill to thank jesus2099.)
An option could also be to prepend e.g. track 1-7 with "Part 1: Medieval church music: " (or just "Medieval church music: "), track 8-9 with "Part 2: Medieval instrumental music: "(/"Medieval instrumental music: "), etc. I’ve seen this done elsewhere for similar track lists.