The cap in question is part of the guitar’s tone circuit, which along with a potentiometer forms a variable low-pass filter. A rich folklore has developed over the years around these circuits ...

A filter that blocks low frequencies and allows higher frequencies to pass through. Such filters are used in devices such as POTS splitters that direct phone and DSL signals to different lines.

But by applying the High Pass Filter in Photoshop CC ... so the ability to apply it sparingly in low-light shots is invaluable. Another plus of sharpening in an indestructive manner on layer ...