Abstract: A box consisting of bottom, side and end walls forms a resonating chamber. An integral sounding panel has thickened ribs on the underside of its ends secured to the tops of the end walls with continuous side strips overlying the tops of the side walls of the chamber in spaced relation thereto. Between the side strips, the panel has three or more spaced longitudinal slots formed therethrough and extending between the ribs on the bottom of the panel. Transverse slots are formed between adjacent longitudinal slots at different distances from the ends of the panel forming vibratory fingers of different lengths. The undersides of the free ends of the fingers have thickened portions which are equal in thickness to the end ribs on the panel, and which extend from the free ends of all of the fingers to an equally spaced distance from the end ribs.