timbre vs tonus

timbre

noun
  • The quality of a sound independent of its pitch and volume. 

  • The pitch of a sound as heard by the ear, described relative to its absolute pitch. 

  • The crest on a coat of arms. 

tonus

noun
  • tonicity; tone 

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