a cappella vs rap

a cappella

noun
  • A vocal performance with no instrumental accompaniment. 

adv
  • In a manner of a choir with no instrumental accompaniment; literally, "in the style of the (Sistine) Chapel (in Rome)", such as a musical Mass done a cappella. 

adj
  • Singing solely or mainly without instrumental accompaniment. 

  • Related to a form of purely vocal music mostly associated with American college performance groups. 

rap

noun
  • Rap music. 

  • A whit; a jot. 

  • A positive appraisal; a recommendation. 

  • An appraisal. 

  • Any of the tokens that passed current for a halfpenny in Ireland in the early part of the eighteenth century; any coin of trifling value. 

  • A charge, whether or not it results in a conviction. 

  • A lea or skein of yarn that forms the standard length taken from the reel, 80 yards of worsted or 120 yards of silk or cotton. 

  • A sharp blow with something hard. 

  • A casual talk. 

  • Blame for something. 

  • A song, verse, or instance of singing in the style of rap music. 

verb
  • To strike something sharply with one's knuckles; knock. 

  • To free (a pattern) in a mould by light blows on the pattern, so as to facilitate its removal. 

  • To speak (lyrics) in the style of rap music. 

  • To seize and carry off. 

  • To transport out of oneself; to affect with rapture. 

  • To talk casually; to engage in conversation. 

  • To utter quickly and sharply. 

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