balladeer vs singer-songwriter

balladeer

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

verb
  • To sing a ballad 

singer-songwriter

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

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