bebop vs plainsong

bebop

noun
  • An early form of modern jazz played by small groups and featuring driving rhythms and complex, often dissonant harmonies. 

verb
  • To participate in bebop jazz, such as by dancing in a way associated with the genre. 

  • To walk in an easygoing, carefree manner. 

plainsong

noun
  • A form of monophonic chant in unison using the Gregorian scale, sung in various Christian churches. 

  • A plain unvarnished statement, without exaggeration. 

  • A cantus firmus or theme chosen for contrapuntal treatment; so called because often an actual fragment of plain-song. 

  • The simple notes of an air, without ornament or variation. 

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