leitmotif vs overture

leitmotif

noun
  • A melodic theme associated with a particular character, place, thing or idea in an opera. 

  • A recurring theme. 

overture

noun
  • A musical introduction to a piece of music, or a play. 

  • A motion placed before a legislative body, such as the General Assembly of the Church of Scotland. 

  • An approach or proposal made to initiate communication, establish a relationship etc. 

verb
  • To make overtures; to approach with a proposal. 

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