choir vs choral group

choir

noun
  • A group of people who sing together; a company of people who are trained to sing together. 

  • The part of a church where the choir assembles for song. 

  • One of the nine ranks or orders of angels. 

  • Set of strings (one per note) for a harpsichord. 

verb
  • To sing in concert. 

choral group

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