cantor vs singer-songwriter

cantor

noun
  • singer, especially someone who takes a special role of singing or song leading at a ceremony 

  • A prayer leader in a Jewish service; a hazzan 

singer-songwriter

noun
  • A musician who both sings and composes, especially when recording or performing his/her own compositions. 

How often have the words cantor and singer-songwriter occurred in a corpus of books? (source: Google Ngram Viewer )