Here I will try to defend
to some extent the role of the so called C note as a so called "octave" range divider.
If look at the "known" reference
A4 = 440 Hz
(which is questionable and not so well defined by anything, but that is another topic)
please, have a look at the following frequency chart for the notes (tones in Music 12-TET system):
You can immediately see that note C at some point equals 256 cycles per second. Let's leave the physics aside for now, though I will explain its role further down (what is a second? and why?).
We know that on average the human hearing range is between 20 ~ 20 000Hz (cycles, repetitions per second of a vibrating object or medium).
Nothing stops us from finding humans who can hear as low as 16Hz or 32Hz - I hope you see where this is going. Because 20Hz is more suitable to note E (under A=440Hz) - if this is where should we start dividing our note ranges.
Tone Frequency chart - link
Lets take the radical approach though. The absolute reference point!
0Hz means total silence, at rest. Then
1Hz would be our note, unit note we might call it. Then
2Hz would be its "octave" (inappropriate term in this case). Then
4Hz, then
8Hz, then...
16Hz... then
32Hz. Ha!
What do we have here, please look at the chart in the link
C = 32.70Hz - quite close! Lets continue.
32 × 2 = 64 × 2 = 128 × 2 = 256Hz
In any step we will fall between what we know as B and C notes. So, there is
the separator.
Here comes the bad design part though... because the standard piano keyboard is a mess!
By pure visual means, on the piano keyboard we've got two point (keys) of symmetry (well, because there are two different rows of two different group of keys by colour, shape size and position in space!).
One point of symmetry belongs to the key for the note
D, and the other (on the black keys) is
6 (= 12 : 2) "semi-tones" ("half-steps"?!) above (or below), resulting on the key for the note
Ab (G#). Well it is the black one...
in the middle... of the sub-group of three black keys.
Symmetry - video link (only about D though)
So, by pure visual means the "octave" separator on the piano should have been either
D or
Ab (G#) (tritone apart).
So there you have it - multiple views and results for a single problem.
Later I will try to explain how this works in the
Plain (Pashkuli) notation System.