::: "Serious dramatic theatre with music, outside the norms of Broadway musicals" is accurate, but is a description, rather than terminology. I would rather spend time enjoying the music than trying to create terminology for it. Then again, I'm not a musicologist. (I'm a composer, if that's of any interest.) Marat/Sade doesn't involve music as far as I can tell. 

 ::: Sorry if anything I'm writing is coming off as antagonistic. I really don't mean for it to be. Again, feel free to write more relating the works mentioned, but I see no wrong in having an unadorned See Also list. It seems to be perfectly reasonable to include a list under Wikipedia guidelines.