hard rock vs soul

hard rock

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

soul

noun
  • Soul music. 

  • The spirit or essence of anything. 

  • The spirit or essence of a person usually thought to consist of one's thoughts and personality, often believed to live on after the person's death. 

  • A kind of submanifold involved in the soul theorem of Riemannian geometry. 

  • A person, especially as one among many. 

  • An individual life. 

  • Life, energy, vigor. 

verb
  • To beg on All Soul's Day. 

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