Mentioned only by Wedgwood, who provides the illustration reproduced here, with the following explanation: Fig B illustrates a simpler, in fact the original, form of Tremulant Diaphone. No examples have actually been used in organs in this country, but this particular form of Diaphone is very successfully used by Voit of Durlach, Germany, as the sole pedal stop (Diaphonic Bassoon) in his small compact organs. The raison d'être of this somewhat singular tonal disposition is to be found in the high efficiency of this stop on a low wind pressure. A specimen, speaking on a pressure of 100 mm. (4 in.) occurs at Luxembourg Church (1902, designed in 1900). . . . The satisfactory working, and the tone quality, depend greatly on the adjustment of the spring s. The name Diaphonic Violone appears only in the caption of the illustration.