While building a small practice amp I did some research into variations on a single tone control as I did not want the complexity of a full guitar tone stack.
After much experimentation I settled on a very simple circuit used in the famous Big Muff pedal from ElectroHarmonix as it provides a wide range of usable guitar tones and works extremely well in the amplifier which is lossely based on the Fender Champ topology. It comprises of 2 filters, one low pass the other high pass, blended together with a potentiometer.
Simulation is dsp code was trivial so I decided to see what I could do with this in some sort of distortion/overdrive pedal simulation. The result is the GxTiltTone valve overdrive. Basically a 2 valve preamp with simple drive, gain and tone control.
By itself it gives a very usable range of distorted and clean tones, put it in front of an amp sim and it nicely overloads the input.
Next step is to try wrapping this valve preamp around a variety of other effects to see what it sounds like.