relax vs tune down

relax

verb
  • To become loose. 

  • To become less severe or tense. 

  • To make something (such as codes and regulations) more lenient. 

  • To calm down. 

  • To relieve (something) from stress. 

  • To make something less severe or tense. 

  • To make something loose. 

  • To become more lenient. 

tune down

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