From Teeth to Rubber (was: What means 'phaselocked'?)

[Matthias]

>>I play a Korg CX-3 organ, which uses the MK50240 top octave chip, and the
>>equal tempered approximations do not seem quite the same or as accurate >as
>>those in the Hammond organ.

>I modded my CX-3 a lot, but this is something still missing. Perhaps
>we'd need a higher master clock frequency and more accurate divider
>circuits (PLL M/N circuits?).
>Can anybody confirm that this is the main difference in frequencies
>of Hammonds and a CX-3 ? I mean, if I would have the right 12
>equally tempered top octave notes, everything else would be like
>in the Hammond? I remember there is *very few* beating in the
>CX-3 even with odd upper drawbars ....
>
>Given the top octave would be generated with M/N PLLs, we could
>even modulate the PLL-VCOs directly.

Fascinating ideas.
I had a M3 and worked on it a lot.

Listening to fixed or free phases is definitally very different and can be
felt even if the Hammond is very low in the mix.

I was not aware that the Hammond  created sound with "tempered harmonics" -
a very weird mixture of physics and Bach, but probably grown with the
ancient pipe organ, that had to educate our ancestors ears!
(ever thought of "synced pipes" or PLP: phase locked pipes ?)
How do the electronic church organs handle this?

Actually this talk about Hammond can be adapted to any instrument. The
computer brings a new acuracy which is marvelous in some contexts for not
existing in Nature. But for my taste, in the case of sound, it only serves
to modify and record, not to oscilate.
The ear seams to be very inteligent and gets tired soon of tooth weel or
digital dividers, even of repeated samples.
Colour comes with incertainty. I call that: Space for the divine.

We have no way to imitate a rubber band gear digitaly (I am not sure its a
rubber band, but as Gene said, with tooth weels you do not get there). The
two weel give a irrational (If I remember math. right: numbers that cannot
be created by division of real numbers) rate and a finite acuracy

The top octave does not need to be VCO. If you want to just modulate a
little with slow noise, you can use a VaryCap diode. Probably you need a
independent noise source for each voice to get the effect.
Tuning without log is easy to get stable.
So with a few chips, you can replace the top octave with 12 INDEPENDENT
analog (rubber!) oscilators and change both characteristics:
*  tempered tuning
*  the unlocked phase.

There might be another problem, because the oscilators of the Hammend are
DEPENDENT, but not acurately. Any idea how to imitate that?
PLL is not the thing, because it locks the phase. But we could discover a
looser way to detect frequency and compare to the tuning of a master
generator. Since the relation of the sub generators is irrational, it
cannot be formed with a divider, but with a FTV-VTF net - probably more
complicated than audible.

The crosstalk and delayed apearence of harmonics due to the switch bars I
would not try to imitate. Its a detail anyway, and maybe not that positive,
if you think in musical and not historical terms.

More important would be the inclusion of lead or granit, because unless it
is very heavy, it does not sound like a Hammond...

I would love to hear such an imitation. A sample does not say anything. You
have play for a while and feel whether its alive or not.

Luck
Matthias

PS
Those polyphonic analogs like OBMx would have the independent oscilators
and processing power to implement what we are talking about. How do they
imitate the Hammond?