music hall vs opera

music hall

noun
  • An auditorium for concerts and musical entertainments. 

  • A vaudeville or variety theater. 

opera

noun
  • A building designed for the performance of such works; an opera house. 

  • A theatrical work, combining drama, music, song and sometimes dance. 

  • The score for such a work. 

  • Any showy, melodramatic or unrealistic production resembling an opera. 

  • A company dedicated to performing such works. 

How often have the words music hall and opera occurred in a corpus of books? (source: Google Ngram Viewer )