hold forth vs sound off

hold forth

verb
  • To talk at great length. 

  • To extend or offer, propose. 

sound off

verb
  • To hold forth about something in an opinionated manner. 

  • Command instructing a person to confirm that they are present or that some other objective has been met. 

  • Command instructing a person to speak up or acknowledge something. 

How often have the words hold forth and sound off occurred in a corpus of books? (source: Google Ngram Viewer )