descant vs singalong

descant

noun
  • A counterpoint melody sung or played above the theme. 

  • A lengthy discourse on a subject. 

verb
  • To sing or play a descant. 

  • To discuss at length. 

singalong

noun
  • A gathering of people who sing together 

adj
  • designed to allow or encourage the audience to sing along 

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