Alexander Roxburgh Grierson, citizen of Castle Douglas, Scotland, filed some "Improvements in Whistles" for a patent, Apr. 30, 1923 (GB214832, reg. May 1, 1924). The invention is a pure metal nose flute, enhanced with an amplification system, formed by a "chamber" covering all the front side of the instrument.
« Referring to the drawings the whistle or instrument consists essentially of two parts, a wind chamber 1, and an amplifying chamber 2. »
« The straight-down back 4 of the instrument and the upwaedly and outwardly bent lower portion 11 of the the amplifying chamber 2 constitute a pit or recess 12 into which the stream of air from the wind chamber orifice 13 rushes. The stream of air above-mentionned immediately proceeds to set up vibrations in the air contained within the amplifying chamber 2, and the opening-out formation of the said chamber amplifies the sound so that the notes originated in the wind chamber orifice or mouth 13 are made richer and fuller. »
The flute is clearly a hand-free instrument, and has been designed to be made in metal, and détails of construction are forecast.
« The pit 12 made by bending the material to the form above described may conveniently be held inside the lower lip 14 and the lower end 15 of the mouth of the amplifying chamber 2 rests upon the chin. »
« The whole instrument may be formed of three sheet-metal stampings, one constituting the front of the wind chamber 1, the back plate 4 and the bent nortions 12, 15, the other two being identical and each comprising a side plate 16 and a slightly-curved nostril plate 6 which directs the air to the aperture 3. »