You can vary the sound of the guitar by changing the tone
control capacitor. A higher value cap will cut more highs, a lower value cap will cut less and be more subtle.
All are miniature Polyester capacitors rated for 50V or more. (a guitar has less than .3 Volt output.)
Capacitors are placed on the tone control pot, usually 250k or 500k, and are in parallel with the pickups.