song vs vocative

song

noun
  • The act or art of 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. 

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

  • 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. 

vocative

noun
  • Something said to (or as though to) a particular person or thing; an entreaty, an invocation. 

  • The vocative case 

  • A word in the vocative case 

adj
  • Of or pertaining to calling; used in calling or vocation. 

  • Used in address; appellative (said of that case or form of the noun, pronoun, or adjective, in which a person or thing is addressed). For example "Domine, O Lord" 

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