level set vs song

level set

noun
  • A state of mutual understanding among parties 

  • An event consisting of level setting 

  • The set of values x for which a real-valued function f(x) is equal to a given constant. 

verb
  • To establish a baseline of mutual understanding 

song

noun
  • An object of derision; a laughing stock. 

  • 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. 

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

  • 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 level set and song occurred in a corpus of books? (source: Google Ngram Viewer )