bar line vs diapason

bar line

noun
  • A vertical line in musical notation used to separate two bars or measures. 

  • Synonym of crossline (“type of headline”) 

diapason

noun
  • The range or scope of something, especially of notes in a scale, or of a particular musical instrument. 

  • A harmonious outpouring of sound. 

  • A tonal grouping of the flue pipes of a pipe organ. 

  • The musical octave. 

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