voltage controlled resistors

[jorgen.bergfors at idg.se]

>This might be a stupid idea, but has anyone ever built a simple "voltage
>controlled resistor" that, with a switch, could override a potentiometer? is
>this possible? it would be nice to have lfo's controlling as many things as
>possible :)

Yes, a Vactrol could be considered a voltage controlled resistor. It has been used in many instances for the application you mention.
http://www.perkinelmer.com/Opto-110/vactrols.htm

/Jorgen