So I went through the chapter again. I actually found an example of octave leaps on all the active tones. On page 18 par. 28:
However I think it's important to into account par.6 in page 6.
So while it is possible to leap an octave whenever (so long as you haven't recently made a wide skip), the tendency and urgency of the active tones should be ...
If you read a book about good melodies and rules for good melodies you will certainly find some advice or rules developed of the cantus firmus era.
Music (and of course the composer) is always working with expectations and surprisings! Why should this not be in a melody?
I remember children songs we sang in the primary school playing with this effect. ...
I think he's suggesting that the melodic leap of an octave behaves much like a repeated tone (octave equivalence). By the way, I recommend book highly. It's a bit old-fashioned (not so much as Geotschius's other books) but one can adapt as necessary.
The human ear can normally hear 10 octaves of C : from Co to C10. If a musical instrument could be exactly tuned to Scientific Pitch where Co=16 Hz up to C10= 16384 Hz then you could probably perfect octave harmony.
There are probably more versions of this than I am aware of but I'll cite 2 or 3.
In the just tuning system the other intervals were chosen to be a rational fraction of the lowest note in the scale (Do). For example the frequency of a fifth (Sol) is 3/2*(frequency of Do), and a second is 9/8*(Do), etc. You can look up the full chart on wikipedia. The ...