Join between two tags

[stefano_mbp]

Hello Simon

I’m trying to define a new tag that is the result of the join between Composer and Grouping
For example : Ludwig van Beethoven Moonlight Sonata ...
I defined a tag named Comp-Work in indexTags
Then in tagValue Comp-Work.default={Composer}
and finally in tagFormat Comp-Work={$Comp-Work$Grouping}
But I can only obtain the Comp-Work tag with just the Composer
What am I missing?

Thank you

Edit in tagFormat Comp-Work.displayFormat={$Comp-Work$Grouping}