In applying pneumatic action to the pedals of a piano, a bellows about -tin. long by l 1/4in. wide, and opening about 1 in., will be needed for each pedal. The bellows is closed by a spring underneath and opened by the downward pressure of the pedal. It is connected with a distended bellows of about the same size under the key: this bellows, being emptied by the action of the pedal, acts on the key by a tracker. The bellows are connected by a compo tube, and the key bellows are in two rows.