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

88 DICTIONARY OF ORGAN STOPS.
Harmonic Pipes.
Pipes so treated as to speak their first upper partial instead of the
fundamental or ground tone. Wood Flutes caused to overblow by means
of a low mouth and copious winding date from a comparatively early period
in Germany (see Flauto Traverso). The idea of employing harmonic
tones for the sake of increased power in the treble of stops, together with
the invention of the method now in vogue for the production of such tones,
is due to the late M. Aristide Cavailld-Coll, having first been embodied in
his fine organ at the Abbey Church of St. Denis, near Paris. By Gavailld's
method, open flue pipes are pierced half way up with one or more small
holes. These perforations have the effect of causing the vibrating air
column in the pipe to split in half and thus to yield its half-length tone, the
octave. The actual length of the harmonic portion (treble) of an open
harmonic stop is thus twice the real speaking length indicated on the
stop label. The first harmonic above that speaking is, of course, the
twelfth. Harmonic stopped pipes overblow into the twelfth (see Harmonic
Stopped Twelfth, Zauberflote). It has erroneously been advanced
that Cavailld-Coll's invention was anticipated by Gabler at the Benedictine
Monastery, Weingarten, (1750). The statement, which is repeated by a
writer in Grove's Dictionary, would seem to be based on the fact that in
the specification of this organ, as given in Hamilton's " Catechism of the
Organ," and also in Hopkins' and Rimbault's treatise, appears the term
Harmonic Violoncello, 8 ft. As a matter of fact this stop was only
rendered harmonic during the restoration of the organ by Weigle. See
Doppelflote, Harmonic Flute, Harmonic Reeds, in addition to
references already indicated.
Harmonic JReecls—See Harmonic Pipes.
Reeds with double-length tubes in the treble. Such pipes, however,
unlike those of harmonic flue stops are not usually perforated in the middle,
as this treatment is unnecessary in the case of reed pipes. Harmonic
Reeds were introduced by Cavaille'-Coll in conjunction with increased
pressure with the object of securing, in the treble, power proportionate to
that of the bass. This conception was further expanded in the system of
reed voicing of George Willis, who employed harmonic reed work not only
for this purpose, but in order to secure also smoothness and breadth of
tone. It is a delusion to suppose that harmonic reeds are necessarily
noisy or unduly powerful—they can, if desired, be voiced softer than
ordinary true-length pipes. As a matter of fact the mere process of
making a reed harmonic, apart from details of winding, tends to subdue its
tone. Granted, however, a moderate reserve of wind pressure, it is easier
to secure due prominence of tone in the treble than is the case with a pipe
of true length. The harmonic structure of chorus reeds enables them to