[sdiy] 60s organ sound

[Harry Bissell Jr]

The individual footages should be roughly sinusoidal
(assuming Vox continental - drawbars etc) so that
mixing the waves will give the desired 'additive
synthesis'.

The mixture footages could be either complex waves
(I doubt that) or a summation of some higher footage
sinewaves, notably from fifths above the fundamental.

The syntheziser cannot quite simulate this... because
there is a difference between summing up a bunch of
square waves and then filtering, and adding a bunch of
sine waves... namely the sine waves do not have
intermodulation products because they are er...sine
waves :^P

Some of these organs have multiple keyboard busses,
that introduce the individual notes in different
orders... usually the eight foot first, followed by a
miz containing a fifth. This will make the attack
sound
VERY hard to get exactly with subtractive synthesis.

If you had set the drawbars for a common harmonic
sequence... like F + 1/2 (2F) + 1/3 (3F) etc... the
output would be a sawtooth in this case...and the
synth could easily copy that setting.  Square waves
would have only odd harmonics... such as the
fundamental plus some of the fifth (mix) footages.

H^) harry



--- "Cornutt, David K" <david.k.cornutt at boeing.com>
wrote:

> 
> From: Antti Pitkämäki [mailto:anpitkam at hotmail.com]
> > Low pass filttering without any 
> > keyboard tracking and maybe with some resonance
> might make 
> > the sound more 
> > "coloured", and less "pure". Of course the Vox
> must be more 
> > complex than 
> > that.
> 
> It's a good thought, though.  Back when I was trying
> to do combo organ sounds with my Juno-106, one
> problem
> I always had was that the high notes were
> ear-piercingly
> bright.  I had a feeling that it needed some kind of
> fixed low-pass filtering, but playing around with
> graphic EQs, I never got it quite right and I never
> figured out why.  A good combo organ can play those
> high notes without hurting your ears.  Idea: I
> wonder
> if there is some slew rate limiting going on in the
> preamp or amp circuits?  Would have made sense back
> when these things were built, because most of the
> time
> they would have been played through guitar amps that
> couldn't do high slew rates.
> 
>