keynote vs sheet music

keynote

noun
  • The note on which a musical key is based; the tonic. 

  • The main theme of a speech, a written work, or a conference. 

  • A speech that sets the main theme of a conference or other gathering; a keynote speech or keynote address. 

verb
  • To deliver a speech that sets the main theme of a conference or other gathering. 

sheet music

noun
  • Handwritten or printed form of musical notation. 

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