Abstract: A hand-held, manually operated percussion instrument comprises a main body member formed of resilient material and incudes a sidewall portion and an end cap portion which are integrally connected and sealed together to define a continuous concave interior chamber. A base edge of the sidewall portion circumscribes an opening into the interior chamber. A sealing cuff of resilient and compressible material is attached to the base edge. A flattened interior end wall surface extends generally in parallel and planar spaced apart relation from a plane defined by the sealing cuff and base edge. In use, the percussion instrument is moved through the air with the concave interior chamber facing the chest wall of a human individual to whom respiratory therapy is applied. Upon contact with the chest wall, the sealing cuff compresses and seals against the chest wall.