AW: Vocoder Idea

[Haible Juergen]

	> That is, if you're trying to emulate normal vocoder operation.

Yes. Normal Vocoder operation is a good start to create
a lot of extremely un-normal sounds.

	>But the idea of inserting S&Hs into the channels' VCA control
signals
	>may produce some interesting FX (well, I guess it won't improve
speech
	>quality :-)   Has anyone tried something like that?

The Powertran / ETI / Elrad vocoder, and most probably the EMS
vocoders as well, had a Sample&Hold stage for each channel.
It "only" was used for Slew Control and Freeze functions, however.
(i.e. for all channels in common).
On a patchable Vocoder, you can hook up external S&H's of course.

	>BTW, what about completely _synthesizing_ the control signals, e.g.
using
	>a shepard generator and thoroughly mixing up the channel
numbers...? Or
	>multiple random voltages in the LFO freq range (as used in the good
old
	>Elektor Formant).

Sure, but you don't need a Vocoder for that. A simple filter bank plus
a set of VCAs is enough. I do this with a (clone of the) EMS 8 Octave
filter bank all the time. This method has its right on its own.
The great advantage (or, better, a different approach) of the vocoder
is that you replace a Vector of N separate control voltages by the spectrum
of one single audio signal. 

	JH.