balladeer vs songster

balladeer

noun
  • A singer, particularly a professional singer who performs ballads. 

verb
  • To sing a ballad 

songster

noun
  • A man who sings songs, especially as a profession; a male singer. 

  • One who writes songs. 

  • A male songbird. 

  • A book of songs; songbook. 

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