downcast vs singing the blues

downcast

verb
  • To cast from supertype to subtype. 

  • To taunt; to reproach; to upbraid. 

adj
  • Feeling despondent. 

  • Looking downwards. 

noun
  • A ventilating shaft down which the air passes in circulating through a mine. 

  • A cast from supertype to subtype. 

singing the blues

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