Classical music pieces are written by the composer as a work containing multiple movements but sometimes there is more complex hierarchy. Most notably Operas are generally of the form Opera, Acts, Scenes.
For most classical music cases each movement maps to Movement field and Title field, and the work maps to Work field, the Overall Work field has the same value as the Work field.
With operas the scenes map to Movement field and Title field, each act maps to a Work field, and the opera itself maps to Overall Work field. This is as long as Opera Work Format is set to Use MinimServer format (Work Overall Work), there is a conflicting alternative setting required if using Roon.
You can add both levels to the Work index as follows:
IndexTags:Work
itemTags:Overall_Work
tagValue:Work.merge={Overall_Work}
We use merge to add both Work and Overall Work if different, we want to add both values in this case.
MusicBrainz Work
Also sometimes a work can just be a single piece of music without movements. This is usually the case for popular music that is still written and composed. We can include these works as well as follows:
IndexTags:Work
itemTags:Overall_Work, MusicBrainz_Work
tagValue:Work.merge={Overall_Work, MusicBrainz_Work}
There are some differences between the Group field and the Work fields. Sometimes movements are not listed contiguously within an album. MinimServer does not support non-contiguous Groups, but there is no such restriction on MinimServer Works.