The last word on organic synths? (was: Re[3]: Fourier...

[Bob.Schrum at harpercollins.com]

     This thread should move to the Hammond forum--you will definitely get 
     your answer there, but I am sure there is no phase lock.  My 
     recollection is that there are at least 12 axles with gear reduction 
     connecting them, providing rotational speeds in equal tempered 
     intervals.  Each axle has metal wheels with N, N^2, N^4, N^8,... 
     equally-spaced teeth to reproduce that note/harmonic in various 
     octaves.  As a result, octave intervals loosely have the same phase 
     relationship--the wheels' friction linkage to the axle makes this 
     inconsistent.  Non-octave intervals are essentially free-running.
     
     If all the wheels were on a single axle, some of them would have an 
     oddly-sized tooth, which would make a periodic glitch in the sound.
     
     This is still a large oversimplification of the process, because there 
     is other strangeness due to manufacturing limitations.  If you are 
     really interested in this, you're best talking to the Hammond forums.


______________________________ Reply Separator _________________________________
Subject: What means 'phaselocked'?  (was: Re[3]: Fourier-Analysis and
Author:  mz at bacher.co.at (Michael Zacherl - Bacher Systems EDV GmbH) at 
Internet-Server
Date:    5/30/96 7:48 PM


As far as I can recall all tonewheels sit on a single axle.
So if you got two different signals which have nothing common except that 
both are strictly periodic there's a point where they meet again and again.
     
You'll here a constant beating (depending on the signals of course).
If the beating would change (in any measureable not only audible way) there 
would be no 'locking'.
     
So my question: Is this phaselocked or not? 
     
Thanks for your inputs ...
     
/mz
     
     
>      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!
> 
>