touch a chord vs touch a nerve

touch a chord

verb
  • Synonym of strike a chord 

touch a nerve

verb
  • To make a remark or perform a deed which produces a strong response, especially an emotional response such as anxiety or annoyance, because it calls to mind something which has been a source of concern or embarrassment. 

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