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Chapter 15 Vintage B3 427
B3 and Leslie information
Additive synthesis with draw bars
The Hammond B3 is the classic draw bar organ. As with an air-driven pipe organ, the registers
(draw bars, or “stops” on a pipe organ) can be pulled out to engage them. In contrast to a pipe
organ, however, the B3 allows seamless mixing of any draw bar registers. The closer toward you
that the draw bars are dragged, the louder the corresponding tones.
Despite characteristics such as key clicks, variable intonation, distortions, and crosstalk (all of
which Vintage B3 emulates), playing a single note, with a single register, results in a pure sine
tone. Mixing sine tones results in more complex harmonic spectra; this is known as additive
synthesis. Organs—even pipe organs—can be regarded as additive synthesizers. Several
limitations should be considered before viewing the instrument in this way. These limitations, on
the other hand, constitute the charm and character of any real musical instrument.
The naming of the draw bars is derived from the length of organ pipes, measured in feet ('). This
naming convention is still used with electronic musical instruments.
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Halving the length of a pipe doubles its frequency.
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Doubling the frequency results in an upward transposition of one octave.
The lowest register—16' (far left, brown draw bar)—and the higher octave registers—8', 4', 2',
and 1' (white draw bars)—can be freely mixed, in any combination. 16' is commonly described
as the sub-octave. With the sub-octave regarded as the fundamental tone, or rst harmonic, the
octave above 8' is the second harmonic, 4' the fourth harmonic, 2' the eighth harmonic, and 1'
the sixteenth harmonic.
With the 5 1/3' register—the second brown draw bar—you can add the third harmonic. This
is the fth above the 8'. Basically, the draw bars are arranged by pitch, with one exception. The
second draw bar (5 1/3') sounds a fth higher than the third draw bar. See The residual eect on
page 428 for an explanation.
The 2 2/3' register generates the sixth harmonic, 1 3/5' the tenth harmonic, and 1 1/3' the
twelfth harmonic.
An electromechanical tonewheel organ oers the choice of the following registers/harmonics: 1
(16'), 2 (8'), 3 (5 1/3'), 4 (4'), 6 (2 2/3'), 8 (2'), 10 (1 3/5'), 12 (1 1/3'), and 16 (1'). As you can see, the
harmonic spectrum is nowhere near complete. This is one of the main reasons for the common
practice of using overdrive and distortion eects with electromechanical tonewheel organs—
they enrich the harmonic spectra by generating more harmonics.
Note: 2 2/3' is the fth over 4'. 1 3/5' is the major third over 2'. 1 1/3' is the fth over 2'. In the
bass range, this can lead to inharmonic tones, especially when playing bass lines in a minor key.
This is because mixing 2', 1 3/5', and 1 1/3' results in a major chord.