[chuck-users] driving filter frequency from an envelope?

[Robert Poor]

What's the chuck'ian idiom for driving a filter frequency from an  
envelope?

Assume I have a primary signal chain that looks like this:

Blit b => ResonZ z => Envelope e1 => dac;

And I want to drive the center frequency of the ResonZ with another  
envelope.  I know I could do it something like:

Phasor constant => Envelope e2 => blackhole;
constant.phase(1.0);

... and pepper my code with short delays that update the resonator's  
frequency:

     ...
     .01::second => now;
     z.freq(e2*440.0 + 100);
     ...

but that seems both inelegant and computationally wasteful.  I've  
looked at the .op inputs -- that may be the answer, but I can't quite  
tell from the documentation.

So: is there a way to directly control the resonant frequency at the  
UG level without breaking back into "user code"?

Thanks.

- Rob