hip-hop vs rap music

hip-hop

noun
  • An Afro-American urban youth culture based on rap music, breakdancing etc. 

  • A form of popular and dance music featuring strong percussion and a powerful rhythm, usually accompanied by rapping. 

verb
  • To move by hopping or with a hopping motion. 

  • To perform hip-hop music. 

rap music

noun
  • Hip-hop music, especially when focused on rapping. 

How often have the words hip-hop and rap music occurred in a corpus of books? (source: Google Ngram Viewer )