*different multiple artist splitter fields: orchestra, ensemble, soloist (including the ability to specify voice/instrument, which would dovetail with TMCL tags), chorus, choirmaster, etc. For those who like to include ALL the performers, this would cut way down on the need for custom tags.
+1
I think that an option is something like the Artist Tag. It uses a multiple artist splitter, and you can specify the name and the role.
This way you could filter by roles, and not only by artist names.
I'm now using a custom tag (Musicians Credits List) with a Artist (role) pattern, and semicolons, but it is not too useful to filter by roles.
This approach is useful for other genres (for me, as a Jazz lover too, it would be an incredible improvement).