Somone on AH asked for an example of using voltage control on filter resonance. Cynthia of modular synth maker
Cyndustries answered.
From Cynthia on AH:
http://www.cyndustries.com/audio/SynthaCon5.mp3
Here's an example using a Cynthia brand Synthacon Filter set at a fixed
cut-off frequency with the initial Resonance knob set just below
self-oscillation. A fluctuating Sample & Hold voltage is fed into the
VC Resonance Input, which creates the "bubbling resonance" sound.
Some of the random voltage levels from the S & H are not enough to
kick it into oscillation, and many of them are...
(If one were to add just a touch of modulation to the cutoff frequency
and a little reverb as well, then you might have a fairly realistic
tribal "talking drum" type sound).
Most often envelope generators are either connected to VCAs to control
volume, of to VCFs to control the cutoff frequencies. Some intricate
or more sophisticated sounds can be realized when connecting an
additional envelope generator just to control the Resonance parameter
while the usual envelopes are doing Amplitude and Frequency. With all
three envelopes set slightly different from one another, more nuances can
happen within your sonic event. (If you don't have VC resonance, well
then try the third envelope on a VC flanger because that can be lots
of fun too!)
Cynthia
http://www.cyndustries.com/modules_synthaconfilter.cfm