Fourier-Analysis and FM-synthesis

[gstopp at fibermux.com]

     At the risk of being told to take it to the Hammond list, I'd like to 
     add that even though the tonewheels in a Hammond Organ are driven by 
     the same source (the sync motor) via gear shafts, the tones are not 
     really phase-locked in the Fourier sense for a couple reasons:
     
     1. Individual keys share harmonics with different keys, and since the
        generator is equally tempered this means that everything but the
        octaves will drift a little from each other
     
     2. Even the octaves may drift from each other due to mechanical losses
        in the system (the gears are driven by friction drives)
     
     But it definitely falls into the category of early additive synthesis.
     
     Hammond organs might be too analog even for the analog mail list - 
     maybe "organic" would be a better term. Ooooh sorry about the pun....
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re[2]: Fourier-Analysis and FM-synthesis
Author:  Bob.Schrum at harpercollins.com at ccrelayout
Date:    5/30/96 9:39 AM


>> From thierry.rochebois at ief-paris-sud.fr Thu May 30 13:52:34 1996
     
>> This is the very principle of the Hammond organ!
>> This method has been used in electric organs since 1906 (telharmonium). 
>> A multiple VCO versions was developed in 1966 by James Beauchamp.
     
> From mz at bacher.co.at (Michael Zacherl - Bacher Systems EDV GmbH)
     
>Have the VCOs been in phase? As far as I can recall the tonewheels in 
>an early Hammond produced phaselocked harmonics.
     
Not only that, but the harmonics were 12-tone equal-tempered!  That's a 
prime reason why nearly every synth B3 emulation falls short.  Only those 
with top-octave dividers or the Voce V3's 91 digital oscillators (do they 
do this with software or an ASIC?) do justice.  
     
Ah yes... the good old days when you had to oil your "oscillator bank"  
every six months!  Is that analog or what?  :-)  They even had voltage 
control of sorts--just whack wthe AC power switch around for the wildest 
pitch bend you've ever heard!