Standard audio low pass filters tend to work by adjusting the corner
> instead of the roll off or in some sense a one sided Q. So your
> standard treble control is a simple RC low pass filter with R being a
> pot. We have been conditioned by years of use to understand how these
> filters work but they are not the only ones.
>
> What about changing the roll off rate instead or as a combination with
> the corner? =A0Something that shifts the corner and increases the roll
> off? I suppose this is hard to realize in hardware because it requires
> a way to vary between a large number of poles smoothly? At least in
> the analog domain.
>
> I wonder what such filters would look like and sound like?
You can make such a beast uses voltage controllers amplifiers (really variable OTA). Probably googling voltage controlled filter will get you started on the search. Curtis Electromusic made such chips, but of course DSP took the market.
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I'm sad to hear Doug died. I used to do contract work for him. Damn nice guy that would do back flips for you if you treated him right. When he fired someone, trust me, they deserved it.
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I think the variable Q is what you are after:
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