off-key vs out of tune

off-key

adv
  • With inaccurate pitch. 

adj
  • Pitched inaccurately either above or below the correct note. 

  • Not harmonious, or out of accord. 

out of tune

prep
  • Not in agreement or in harmony (with something). 

  • Not in the correct musical pitch. 

How often have the words off-key and out of tune occurred in a corpus of books? (source: Google Ngram Viewer )