This photo shows a key pushing down on two conductive leaf springs stacked beneath it. Two nylon strips run
below the springs,
each holding a thin bus wire.
When a key is pressed, each leaf spring touches and applies a
to one of the buses.
One contact passes a voltage proportional to the note. A few
milliseconds later, the other contact passes a voltage to trigger the
sound of that note.
The first step in cleaning contacts is to brush away
loose dirt and debris from around the contacts. Use a small paint brush,
or compressed air.