bebop vs hard rock

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. 

hard rock

noun
  • A rock music genre marked by a heavy regular beat, high amplification, and usually frenzied performances. 

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