Hammond Model A Manual page 12

A Chorus Control drawbar is provided whereby the organist can turn
this new effect on or off at will.
The Chorus Generator makes possible a large number of pleasing ensemble
qualities. The familiar Voix Celeste and Unda Maris are two of many
useful organ stops which utilize the same principle involved in the
Hammond Organ chorus effect. String combinations, both solo and en-
semble, assume a new depth and beauty. Hitherto, it has been customary
to limit such an effect to one or two tonalities. In the Hammond Organ,
the chorus effect may be on any or all tone qualities. The tremulant
takes on a new charm when used with the chorus effect. When the full
organ is used, an added richness and fulness of tone will be instantly
observed: an effect of tone emanating from many sources.
The Chorus Generator has been so designed that combinations of a
dignified character, such as Diapasons and large scale Flutes are not affected
to the extent of the string and reed qualities.
Installation problems will be materially reduced, for the Chorus Effect
does much to overcome the disadvantages of smaller rooms or those
presenting a "dead" or non-reverberating condition.
The Chorus Generator Unit has its own starting and running motors
which operate simultaneously with the motors of the main generator.
For each of certain tone-wheels in the main generator there is in the chorus
generator a pair of tone-wheels which have their speeds so adjusted that
one will produce a tone slightly sharp and the other a tone slightly fiat
by comparison with the accurately tuned main generator frequencies.
Thus, when the chorus generator unit is turned on and a single frequency
sounded from the main generator, the two slightly de-tuned chorus fre-
quencies will also sound and the result is the formation of a complex series
of" beats " or " waves " in the tone.
The chorus control is a black drawbar situated at the right of the console
lust above the end of the harmonic controllers. When the chorus control
is drawn out, the chorus generator unit is switched on. Pushing the
control in disconnects the generator unit so that the chorus effect is not
heard.
GENERAL.
The above should serve to give the artist an idea of the vast resources of
the Hammond Organ. Within each tone family can be discovered an
infinite variety of qualities from which the player can choose; he is
not limited to relatively few in each family, but is enabled to create that
special subtlety of tone-colour which he may want at a particular moment.
It is this which makes the Hammond Organ the instrument upon which
the artist-organist can best express his own individuality.
THE HARMONIC CONTROLLER FOR THE PEDAL ORGAN.
Here the harmonic resources have been combined into only two harmonic
controls. The fundamental 16 ft. pitch and second harmonic are
associated with the left-hand control and produce the fundamental depth
to the pedal. The third, fourth, fifth, sixth and eighth harmonics are
associated with the right-hand control to give higher harmonic quality
variations, and a useful 8 ft. solo if used without the left-hand control.
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