Capacitors are a necessary component used as part of a guitar's tone control circuit. Generally, the value of the capacitor determines the amount of treble that is cut when the tone knob is turned down. For example, a .047uf capacitor will "roll off" more treble than a .022uf capacitor. The .001uf capacitors are mostly used between the hot terminals of the volume potentiometer to create a treble boost as you turn the knob down.