Thank you Nigel, RB-J, Steffan, and Neil.

i suspect that those tone wheel waveforms are close to sinusoidal.

Early models were.  Starting I think around '53 with the B-3, C-3 and A1xx
series (A100 etc.) they were a bit brighter, and the foot pedals were FAR

> but to find out from your .wav file, you can apply a pretty simple pitch
> detection to get the period of the waveform to a precision of
> fractional sample.? then you can divide that period into N samples using
> interpolation and resampling techniques.? this is how i would advocate
> extracting a wavetable from a portion of a note (as opposed to the
> heterodyne oscillator approach).

Exactly what I've already coded!  Curious what the heterodyne oscillator
approach is, but don't tell me, I'll look it up myself, thx as always.

how did you record the signals? If taken from the TWG terminal strip, they
> contain also a ton of neighbor frequencies, sub-harmonics, etc.

A social network acquaintance supplied me the recording.  I'm not sure
where they tapped in to get it.  What it DOES have--and I'm glad of it--is
the leakage from the neighboring disk.  The disks are basically all in
little compartments of two disks, 4 octaves apart, and each disk is picked
up by the other's pickup to some extent.  It's absolutely audible, maybe
-36dB down or something.  Since the two disks are locked in frequency,
though, I'm just incorporating the partner into the wavetable, so it has
zero performance penalty while playing.  (My synth calculates the wavetable
contents when a patch is loaded/parsed, so it takes an extra few tenths of
a second should you change the leakage coefficient, which will be
user-editable but not in real-time.)

And why do you need the _exact_ frequencies?

Only to have the exact wavelength, so I can do a DFT and get the exact
harmonics from each disk and the amount of leakage.

> Happy new year and all the best!

To you too, Staffan!

The tonewheels are intended to be perfectly sinusoidal, though their mass
> stamping does introduce various differences. The exception is the lowest
> octave of certain models, B3 included, made at certain times, as described
> here:

My understanding is that the first Hammonds up to the but not including the
B-3/C-3/A1xx models, were nearly sinusoidal, but after that they were
brightened considerably and that's what I'm seeing in my recording.

> Given the intent of the tonewheel, I wouldn't bother with this particular
> experiment at all if I were trying to recreate a B3.  But then, I wouldn't
> do any foldback either.

Hey, if you don't want an actual Hammond, that's why I wrote the entire
soft synth in the first place!  :-D

The main reason I'm doing this patch is as a case study showing my soft
synth can emulate a real Hammond (and Leslie) warts and all, to a very deep
level, and showing how one would go about it.

But it's also well-known that every tonewheel
> organ has its own character due to being a very complex electro-mechanical
> device, so I suppose I might try this analysis if I were attempting to
> create a framework for creating such differenced organs.

The more modern "clonewheel" organs do let you simulate each wheel's
harmonics individually, etc.  In fact I should go look at a Hammond XK-5
just to see if my research is similar to their default settings.

It'd be interesting if a clonewheel manufacturer had an automated service
whereby you upload a recording as I requested of my organ acquaintance,
then let you download a patch that matched that exact organ.

Thanks again, all.
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