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

158 DICTIONARY OF ORGAN STOPS.
of amelioration. The late Mr. Henry Willis in 1853 patented a form of
Tremulant, the speed of which was capable of modification according
to the degree of depression of a pedal. Mr. Casson in 1889 introduced
another variety, yclept "Vibrato," a silent Tremulant of delicate beat,
varying its speed according to the position of the Swell louvres (Omagh,
Ireland). The artistic value of this device cannot be overrated. The
dead beat of a Tremulant running at one speed tends to ruin the effect of
a slow and impressive smorzando—especially on a dull-toned stop, such
as a Gedeckt or Harmonic Flute. The Austin Organ Co., of Hartford,
U.S.A., employ a " Fan Tremolo," somewhat similar to that employed in
American suction organs. It consists of a double-bladed fan suspended
over the pipes, and is driven by four motors coupled in pairs and actuated
by the pipe wind. The effect of this Fan Tremulant is musical and
pleasing, the sound waves being acted upon after generation. The beat
is less pronounced in the bass, and does not partake of the heavy sledgehammer
thump which so rapidly becomes wearisome to the ear (See
Bockschwebung). There is an example at the Baptist Church, Rushden,
Northampton. Mr. Willis sometimes secured very satisfactory results merely
by the employment of a large free-reed inserted in the wind-chest. Most
modern Tremulants are so constructed that their speed is adjustable from
within the organ. The Vox Humana requires a Tremulant of rapid beat
a Vibrato, in fact—but in the case of most other stops, whether flue or
reed, one of less rapid pulsation is ordinarily conducive to superior results.
Of course, those good folks obsessed by the idie fixe of rigidly austere
and orthodox " legitimate " organ music, those who will brook no such
sacrilege as an "orchestral transcription," regarding the organ as a mere
mechanical machine for the grinding out of stoichiometrically accurate
counterpoint, find themselves unable to tolerate the imbecile mock-pathos
of the Tremulant. At the risk of incurring the ridicule of these puristic
Hobbites, let it here be suggested that a well equipped organ might
profitably include two varieties of Tremulant, one of the vibrato or fan
type, and one of powerful, slow pulsation. (See remarks under Viole
d'Orchestre). That stops under the influence of the Tremulant should
never systematically be combined with those not so affected is an
injunction, the wisdom of which is self-evident.
Tremulants frequently have the undesirable defect of unduly disturbing
the pitch of the stops they affect. On arresting the action of the Tremulant,
it will be found that the pitch of such a stop as the Vox Humana (the
pipes of which exercise but little control over the tongues), for instance,
will sometimes have been deflected to the extent of nearly a quarter of a
tone. This fault may probably be attributed to the very powerful springs
often attached to Tremulants. Difficulty is sometimes experienced in
inducing Tremulants to act, when the organ reservoirs are of the single-rib
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