What?
Special
pseudo-additive synthesis? What’s that?
Well,
additive synthesis is well known: it’s all about adding signals, mostly sine
waves, to create a sound and its harmonics. In the Hammond organ the signals of
the tone wheels are used and are mixed together by setting the drawbars.
Is an
emulation possible in the NordLead? Four Slots can be loaded with four sine
waves (Osc 1) which are mixed to one sound setting the Gain parameter. There is
also the possibility to add an extra four triangle waves (Osc 2) and by using
OscMix an eight tones additive mix is archived. But there it ends… Anyway, why
call this ‘pseudo’? It’s real additive synthese, isn’t it?
Clavia
uses not real additive synthese, but a more obscure and somewhat ‘hidden’
methode, which uses besides a triangle wave form (Note this kind of synthese
was developed to the NordRack, which hasn’t the sine wave yet*) the 50% pulse
wave form, the Filter and its Resonance parameter. Why the pulse wave form? It
possesses only the odd harmonics, so the even ones don’t have to be filtered
out.
Filtering
without any Resonance delivers the following waveforms (the Cut-Off parameter
is given in NordLead values = read able after using [Shift+LFO1WaveForm]):
Filter
open [127]
[70]
[50]
There
appears to be almost a perfect sine wave form… Of course in pseudo-additive
synthese it’s not this sine wave that will be used, but the wave forms which
are a little bit less filtered out. These Filter setting also works to Osc 2,
which can be set to another Semitone setting, mostly a higher frequency, but a
lower one works too! The use of other wave forms and Osc 2 is a nice option,
like the triangle is used to make just a single harmonic. Scrolling to the
factory presets sometimes Osc 1 produces the pulse wave and Osc 2 makes the
triangle and sometimes the other way around. Simple said the filtered pulse is
capable of producing a more complex sound which resembles a part of the
additive synthese already and Osc 2 is used because it can be tuned to Osc 1. So
sometimes both oscillators are set to the same wave form.
Octave
Shift in another Slot is a simple way to create other parts of the harmonics. That’s
why these sounds are Performances instead of single Programs.
Tweaking
the Resonance brings in other waveforms, like:
adding some Resonance
After
doing some fine tuning two or three Slots are capable to reproduce most of the
sounds of the Hammond organ.
Clavia
also introduced also a way to mimic the effect of a Lesley box. The NordLead
organ sounds use only one Slot in Unison, which is the Slot producing the mid
range sound (More Slots set to Unison will limit the number of Voices). Another
nice part of the Lesley effect is created by Puls Width Modulation controlled
by LFO1: the swinging impression of the horn. Some very little detuning
(beating) of the Fine Tune makes a strong effect too.
If you
like the organ sounds don’t forget to experiment with these Performances. My
favorite is H2, activate Slot A and tweak the Filter Cut-off while playing and
you’ll understands what "The organ grinds" means J If you know how to tune it, the RingModulator can be
a revalation too!
The next
example uses the ModEnv which allows to start a high speed Lesley which is
slowed down soon, but starts again when playing the next key.
Other
effects which can result in nice effects are Distortion added to one or two of
the Slots and of course some Frequency Modulation.
Using the
Amplifier Envelope makes it sound more a synthesizer then an organ. Default
setting is ‘all zero, only Sustain set to max’. Some small amount of Attack and
Decay without any Sustain can be used to add a Percusive like sound.
* Just
for the record… Hammond Tone Wheel Generators doesn’t produce sine waves but
triangles J