heavy metal vs song

heavy metal

noun
  • A genre descended from rock music, characterized by massive sound, highly amplified distortion, and overall loudness, often with extended guitar solos, and lyrics that involve aggressive or fantastic imagery. 

  • Any metal that has a specific gravity greater than about 5, especially one, such as lead, that is poisonous and may be a hazard in the environment. (There are many different definitions of what counts as a heavy metal; see Heavy metals for a discussion.) 

  • Great influence or power. 

  • guns or shot of large size. 

song

noun
  • A musical composition with lyrics for voice or voices, performed by singing. 

  • A low price, especially one under the expected value; chiefly in for a song. 

  • A melodious sound made by a bird, insect, whale or other animal. 

  • An object of derision; a laughing stock. 

  • Poetical composition; poetry; verse. 

  • The distinctive sound that a male bird utters to attract a mate or to protect his territory; contrasts with call; also, similar vocalisations made by female birds. 

  • Any musical composition. 

  • The act or art of singing. 

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