sing-song vs unchanged

sing-song

noun
  • A kind of verse with a simple, song-like rhythm. 

  • An informal gathering involving group singing. 

adj
  • Like a piece of sing-song; simple and melodic, song-like. 

unchanged

adj
  • Not changed or altered; remaining in an original state. 

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