dead march vs threnode

dead march

noun
  • A mournful, deliberately-paced musical work suitable for a funeral or remembrance ceremony. 

  • Any of several particular notable musical works of this kind, such as the Marche funèbre by Frédéric Chopin or the funeral anthem in George Frideric Handel's Saul. 

threnode

noun
  • A threne, or threnody; a dirge; a funeral song. 

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