psalm vs psalmody

psalm

verb
  • To extol in psalms; to make music; to sing 

noun
  • A sacred song; a poetical composition for use in the praise or worship of God. 

  • One of the hymns by David and others, collected into one book of the Old Testament, or a modern metrical version of such a hymn for public worship. 

psalmody

verb
  • To celebrate in psalms. 

noun
  • A collection of psalms. 

  • The singing or the writing of psalms. 

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