AW: Linear/Exp Filters, was Re[2]: VCOs as modulation sources

[Haible_Juergen#Tel2743]

> Are there any existing designs for a 4-pole resonant filter that can be
> controlled by both linear and exponential modulation?

No problem to implement both expo and (simple) linear control,
but ...

> My DX-7 days have got
>me thinking about having a resonating filter in which the output can be
>routed to modulate the filter cutoff in a linear fashion, while the pitch 
of
>the resonance is controlled by a 1V/Oct signal.  If this works anything 
like
>digital FM,

... as far as I can see, it won't come near the FM implemented in a
DX-7. You'd need thru-zero-FM (ordinary linear FM sounds quite boring,
because the modulation index is so restricted). No idea how you could
implement *this* in a VCF !     8-(

JH.