mitigate vs modulate

mitigate

verb
  • To reduce, lessen, or decrease; to make less severe or easier to bear. 

  • To downplay. 

modulate

verb
  • To regulate, adjust or adapt 

  • To change the pitch, intensity or tone of one's voice or of a musical instrument 

  • to vary the amplitude, frequency or phase of a carrier wave in proportion to the amplitude etc of a source wave (such as speech or music) 

  • to move from one key or tonality to another, especially by using a chord progression 

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