Abstract: For recorders and like wood wind instruments various measures have been proposed to overcome the variations in musical tone which derive from the effects of moisture accumulating within the mouth-piece during playing. The provision of a blowing duct of which the surfaces are non-absorbent only leads to musical distortions because of irregularities in the air movements due to moisture droplets. The provision of adhered platelets of absorbent material on the blowing duct surfaces is found to have the defect that the adhesive bond is destroyed by swelling and contraction of the platelets, leading to a reduced useful life of the mouthpiece. The answer has been found in providing a core of dimensionally stable and absorbent material, such as hardened plaster of paris.