lead sheet vs overture

lead sheet

noun
  • A form of written music that specifies the melody, lyrics, and harmony. 

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 lead sheet and overture occurred in a corpus of books? (source: Google Ngram Viewer )