Wedgwood describes this stop as follows, with the accompanying illustrations: In 1897 Mr. Hope-Jones patented an improved variety of Diaphone, known as the Diaphonic Horn, or sometimes as the �valvular reed�. In it the motor bellows is dispensed with, the vibrating pallet or disk being carried on the free end of a spring. It is thus a variety of beating reed. The construction of this form of Diaphone will be explained by reference to Fig. D. The spring is made of aluminium, a pliable metal readily admitting the correct adjustment of the disc in relation to the block against which it beats. Whereas the Tremulant Diaphones are tuned by the resonator or pipe, the valvular reed is properly tuned by the spring and regulated at the pipe.
Diaphonic Horn 16', St. Clement, Ilford (England?).