Treble Bleed - High Pass Filter
Often when turning down the volume of your guitar you will notice that much of your high end (treble) signal vanishes. A way to combat this, and to let some of that lost treble "pass around" the volume pot is to put a capacitor across two lugs of the volume pot. Different cap values will allow different amounts of treble to bleed through the volume pot into your output signal.
A different take on the treble bleed: