Usage example: {{album producer category|Scott Litt}}

produces:

This is a set category. It should only contain pages that are Album producer category or lists of Album producer category, as well as subcategories containing those things (themselves set categories). Topics about Album producer category in general should be placed in relevant topic categories.

See that live at Category:Albums produced by Scott Litt.

Things to do:

• Automatically detect name so that it doesn't have to be entered in field 1. (Use {{BASEPAGENAME}} somehow...?)
• Include default sorting (is this possible? Desirable?) Note that this also puts categories into Category:Set categories--maybe only sort within Category:Albums by producer and leave out defaultsort altogether)
• Include display names (using display= or 2=)
• Include parent categories where they exist (e.g. automatically include Category:Albums produced by Quincy Jones under Category:Quincy Jones)