HAMMOND ORGAN
The
beauty of the Hammond vibrato system is that it produces a very good vibrato
which on its maximum setting is very full and rich sounding. The lower settings
are more subtle but they are also very useful for creating specific effects.
Because the Hammond vibrato system adds the vibrato to waveforms that have
already been produced, it will also add vibrato to any signal which is fed
into the system. Thus, if you desired to run signals from an amplified chime
unit, or a MIDI keyboard, or even another electronic organ whose vibrato is
not as good-sounding, it is easily possible to do this.
So far, we have looked at the basic Hammond
tone generating system, touched upon how the Hammond produces different tone
colors and examined its unique vibrato system in some detail. We should look
now at the means in which the Hammond produces different tone colors in a
little more detail. Below is a picture showing a portion of the keyboards
of a typical tone wheel Hammond console.
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Figure 20, left. This picture shows you part of the keyboard area of a typical Hammond console. The controls just over the upper keyboard are the so-called Hammond harmonic drawbars by means of which the musician selects the individual harmonic pitches which should be present on every key and also the volume at which they should sound. The twelve reverse-colored keys to the left of the keyboards are preset keys. Favorite combinations of harmonic draw-bars can be set up inside the console. Then the simple expedient of pressing a preset key brings up that com-bination.
At the upper left are three white controls. The first one affects the over-all volume of the instrument giving either "soft" volume or normal. The other two controls place the vibrato effect on either keyboard as the musician desires. Roll mouse cursor over picture for details.
The next picture, figure twenty-one below shows you one individual group of drawbars. Notice that each has a label strip with numbers one to eight, representing the eight different volume levels for each drawbar. If a drawbar is pushed all the way in, it connects to ground and the harmonic it represents is not present in the resulting tone. In this picture, the first two drawbars are pushed all the way in to the “zero” position. I placed a sheet of paper under the drawbars in this picture to improve the legibility of the picture.
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Figure 21, right. A single group of draw-bars showing a set-up for a general accom-paniment type tone. Experienced Ham-mond players generally do not memorize the numerical combinations of drawbars but rather go by the shape or pattern that they make. Roll mouse cursor over picture to see individual drawbar harmonic numbers.
Although
these are B&W pictures, the first two drawbars are brown. The next
two are white, the next is black, followed by another white drawbar,
then two more black drawbars and finally one white one. This was a handy
color code that the folks at Hammond developed so that the musician
could tell at a glance what is what. The two brown drawbars are associated
with a tone that is one octave lower than normal. The white drawbars
are all octavely-related frequencies and represent from left to right
respectively the fundamental or first harmonic, the second harmonic,
the fourth and the eighth harmonics. The black drawbars control from
left to right the third, fifth and sixth harmonics.
On a typical tone wheel Hammond console,
there are four groups of drawbars, two groups for each keyboard. The
reason for this is so that the musician can set up two different tone
colors and then switch easily from one to the other. (This in addition
to the preset combinations represented by the other reverse-color keys
at the left end of each keyboard). There are
also two additional drawbars to control the tones on the bass pedals.
By means of a simple wiring change in the console, many Hammond players
create an additional drawbar for the pedals to increase the tonal versatility
of the pedal division. Generally we use one drawbar out of the lower
keyboard for this purpose as it is worth sacrificing control over one
harmonic on the lower keyboard for one drawbar group to gain the additional
control over the pedal tones. Later Hammond organs, such as the H series
and the X66 included extra drawbars for the pedals.
On the next page we have a so-called "take
apart" diagram where you can actually click on the drawbars and,
using typical drag-and-drop mouse techniques, move them in or out to
see how their contacts slide under the associated group of drawbar busbars.
As the drawing exists, it shows five typical drawbars, and the busbar
group. Click on the busbar group assembly and slide it out of the way
to see the individual drawbars. Notice how the contact spring on the
drawbar moves to contact the various busbars which connect to the taps
on the matching transformer and which represent the various harmonic
signal levels from "0" or entirely off to "8" which
is the maximum loudness setting for a particular harmonic.
Note: because this take-apart feature is derived with JavaScript, you
will need to have JavaScript enabled on your computer to see the presentation.
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