tonus vs voicing

tonus

noun
  • tonicity; tone 

voicing

noun
  • The final regulation of the pitch and tone of any sound-producing entity, especially of an organ or similar musical instrument. 

  • A classification of speech sounds that tend to be associated with vocal cord vibration. 

  • A particular arrangement of notes to form a chord. 

  • A phonological process that turns a voiceless sound into a voiced one. 

  • The articulatory process in which the vocal cords vibrate. 

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