Duophonic Keyboard

[jh]

>(I'll bet ARP sales 
>people described that note-jumping thing as a "feature" back then.  >"Yeah, 
>it's our duophonic keyboard with Monophonic Auto-Fat!", or something >like 
>that.)

Well yes it can be a feature indeed. It's great when you have the ringmod
in (or a fuzz connected at the output), as you can phrase "dirty" transitions
between two notes when you play short 2-note bits interspersed in
a monophonic line.

>I know the TVS-1 thing doesn't sound like a really big deal these days, >since 
>this is exactly how all polyphonic synths have behaved since the >introduction 
>of microprocessor-scanned polyphonic keyboards (around 1977 or >>1978), but 
>they did it with simple analog circuits (a kind of variation of the ARP 
>method, with a little more sophisticated logic controlling the S&H's).  

I doubt that part of "analogue". Are you really sure ? It looks too close
to the 4-voice to me ... And didn't the FVS come before the TVS ??

JH.

TVS-1's were a lot more expensive than Odysseys, back then.  I guess this 
keyboard was one of the reasons.

When Oberheim introduced the Four-voice, they implemented a discrete-logic 
version of the Dave Rossum/Scott Wedge-invented polyphonic scanning keyboard 
(still no microprocessor).  Those who are interested in seeing how it worked 
can view the Oberheim FVS-1 schematics at Kevin Lightner's Synthfool.com 
site, or look at Juergen Haible's customized OB four-voice clone keyboard 
scanner at his site (linked at the Synthfool site).

It would be interesting to modify an Odyssey keyboard to function like the 
TVS-1 keyboard.  It wouldn't be too difficult, I think.  (of course, it would 
still be only two oscillators, unlike the TVS-1's four, so you might miss the 
"Auto-Fat"...)

Michael Bacich