You should be able to do that with the filter editor.
For the regexp, you want ^Classical( III)?$
But you can easily select just those 2 genres by "Add multiple condition", select "Any of" and add a condition, select genre, select includes, and then select the genre you want, repeat for the 2nd genre.
The dialog is a bit cumbersome to use though, you can also use the Simple Search widget*, simply typing:
*Sadly I still haven't documented the syntax of the Simple Search widget
For the regexp, you want ^Classical( III)?$
But you can easily select just those 2 genres by "Add multiple condition", select "Any of" and add a condition, select genre, select includes, and then select the genre you want, repeat for the 2nd genre.
The dialog is a bit cumbersome to use though, you can also use the Simple Search widget*, simply typing:
Code Select
genre~"^Classical( III)?$" playcount=0
should work, orCode Select
(genre=Classical | genre="Classical III") playcount=0
*Sadly I still haven't documented the syntax of the Simple Search widget