dialogue vs libretto

dialogue

noun
  • In a dramatic or literary presentation, the verbal parts of the script or text; the verbalizations of the actors or characters. 

  • A literary form, where the presentation resembles a conversation. 

  • A dialogue box. 

  • A conversation or other form of discourse between two or more individuals. 

verb
  • To discuss or negotiate so that all parties can reach an understanding. 

  • To put into dialogue form. 

libretto

noun
  • The text of a dramatic musical work, such as an opera. 

  • A book containing such a text. 

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