postlude vs postscript

postlude

noun
  • A concluding passage of text or speech; an epilogue or afterword. 

  • The final part of a piece; especially music played (normally on the organ) at the end of a church service. 

verb
  • To form a postlude (to); to end with a postlude. 

postscript

noun
  • An addition to a story, play, etc. after its completion. 

  • An addendum to a letter, added after the author's signature. 

verb
  • To extend (a letter or another document) with additional remarks. 

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