 The device consists of a small, foot-operated bellows that pumps air into the player's mouth via a rubber tube, which is fitted with a one-way valve to prevent the air from the player's lungs from passing into the bellows.The aerophor mouthpiece (a small metal reed) is mounted adjacent to the instrument mouthpiece such that the player may receive air through the corner of their mouth without disrupting the embouchure.In some models, the bellows contains a water reservoir and electric light bulb to ensure that the supplied air matches the temperature and humidity of the player's breath.