keynote vs teach-in

keynote

noun

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

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

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

verb

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

teach-in

noun

  • An extended session of lectures or discussions on controversial topics as a form of protest. 

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