Page:Letters to a Young Lady (Czerny).djvu/88

 You are already acquainted with the nature of the perfect octave, from the perfect common chord.

The superfluous octave is a mere passing note, and it may be accompanied by the major third and perfect fifth. The minor and major ninth require the major third and perfect fifth by way of accompaniment, to which may also be added the minor seventh. And from this you may perceive the difference between the ninth and the second.