Resonance info needed

[Grant Richter]

Actually sending feedback through ANY circuit will produce interesting
results.
The polarity of the feedback is important so having an inverter handy will
be helpful.
Good examples are graphic equalizers (you can get them hanging on the edge
of oscillation in
each pass band) and spring reverbs (you can get them to howl liked the
damned).
Be careful of spring reverbs though, I have actually burned out driver
stages this way.
One interesting patch is to place a spring reverb and a filter in a
feedback loop.
This forms sort of a slow oscillator that will try to oscillate and may or
may not succeed
depending on the phase at the various frequencies.

Very organic sounding, if not positively creepy.

Grant

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From: Thomas Robert de Massy <tomasd at axess.com>
To: synth-diy at mailhost.bpa.nl
Subject: Resonance info needed
Date: Friday, May 21, 1999 11:15 AM

Hi,
    Is someone can give me a good explanation on how the resonance in a VCF
works
(from an electronic point of view). Since it's also often called Q, I
thought it was a pass band and that using the resonance knobs you were
changing the quality of the filter, changing the bandwidth. But as I saw on
many synth info pages, they are always talking about using a feedback to
send back the filtered signal in the input. That's the part I have some
difficulty to understand. I think a simple resonance filter schematic could
help me figure out how it works, it seems very simple but I need more info.

Thanks
          Thomas