descant vs psalmody

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. 

psalmody

noun
  • The singing or the writing of psalms. 

  • A collection of psalms. 

verb
  • To celebrate in psalms. 

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