A comprehensive dictionary of organ stops - Allen Organ Studio of ...

above stops are all of the bivalvular
type illustrated in Fig. A.
m is a motor, to the tail-piece of
which is attached a rod bearing the
compound and spring valves v, v 1
,
working against the springs s, s 1
. On
the admission of wind (under pressure)
to the box a, the motor m is caused
to collapse, and thereby to open the
valves v, v 1
. Wind then rushes into
the chamber b, and, entering the in-
terior of motor m through the passage
c, equalizes the pressure on the motor.
The action of the springs now serves
to close the valves v, v ', and to open
out the motor m, whereupon the pro-
cess is repeated.
DICTIONARY OF ORGAN STOPS. S»
Fig B illustrates a simpler, in fact
the original, form of Tremulant Dia-
phone. 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'etre
of this somewhat singular tonal dis-
position is to be found in the high
efficiency of this stop on a low wind
pressure. A specimen, speaking on
a pressure of ioo mm. (4 in.) occurs
at Luxembourg Church (1902, de-
signed in 1900). The action of the
Diaphone shown in Fig. B will be
explained by reference to the descrip-
tion of Fig. A. The satisfactory
working, and the tone quality, depend
greatly on the adjustment of the
spring s. This spring might be at-
tached to the valve, similarly to one
of the springs shown in Fig. A.
Fig. B.
Diaphonic Violone or Bassoon.