Potentiometers A potentiometer works like a variable resistor. It s the same kind of component that controls level and tone in a guitar or amp. Conductive plastic pots are often used in audio applications thanks to their low noise, infinite resolution and long working life. Power ratings are less good. A pedal pot should have a long working life , but will of course cost more because of this.
Pots tend to oxidize after a few years, causing noises when turned.
A dirty or oxidized pot can be temporarily cured by spraying it with contact spray and turning it back and forth a few times. You d get the strongest level without any volume pot at all. Active EMG pickups use only 25 kOhm, I believe. Impedance is frequency-dependent, meaning that the resistance varies with the signal s frequency. That s what happens when you turn down the level pot on a guitar and the treble decrease at the same time.