We're all familiar with a guitar or bass that picks up EM noise and produces
a steady buzz through the amp. The noise goes away when the player touches
some grounded piece of metal on the guitar, or the strings if the bridge is
grounded.

My question is why does touching a ground point eliminate the buzz? What is
the player's body adding to the circuit in electrical terms? Is it just like
adding a big capacitor between ground and... what, air? Or could it be that
grounding the player allows the player's body to soak up some of the EMI and
reduce the amount reaching the pickups?

Just curious,
Sean