Wah Pedal Guitar Effect Circuit

This is a design project for guitar effect called Wah Pedal Effect. Wah Pedal has been desing around since at least the early 60’s. The Vox is one of brand guitar effect which  is give beautiful sound and simple, only a couple of transistors and an inductor. The really pertinent question that had puzzled many people - including especially me - is how do you get a moving resonant frequency out of a fixed inductor and a fixed capacitor? How does that silly two-transistor Wah Pedal circuit get a moving band pass out of a circuit that changes neither the inductor value or the capacitor, but only what amounts to a volume pot? This  is the figure of the circuit;