bellow vs sing out

bellow

verb
  • To shout in a deep voice. 

  • To make a loud, deep, hollow noise like the roar of an angry bull. 

noun
  • The deep roar of a large animal, or any similar loud noise. 

sing out

verb
  • To call out; yell. 

  • To start singing. 

  • To cry out in pain. 

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