Music drama \Mu"sic dra`ma\
   An opera in which the text and action are not interrupted by
   set arias, duets, etc., the music being determined throughout
   by dramatic appropriateness; musical drama of this character,
   in general. It involves the use of a kind of melodious
   declamation, the development of leitmotif, great orchestral
   elaboration, and a fusion of poetry, music, action, and scene
   into an organic whole. The term is applied esp. to the later
   works of Wagner: "Tristan und Isolde," "Die Meistersinger,"
   "Rheingold," "Walk["u]re," "Siegfried,"
   "G["o]tterd[aum]mmerung," and "Parsifal."
   [Webster 1913 Suppl.]