10
results are obtained with minimal detuning. You may also
need to reduce the second VCO‘s level a little (TP007). To be
honest, though, this really is a matter of personal taste.
Pulse waveforms, unlike periodic square waves, describe
the percentual relationship between the wave’s peeks and
troughs. As a rule of thumb: moving further away from the
consistent square oscillations (50%) results in an ever more
nasal sound. Pulse widths less than 10% are – musically
speaking – less prolific. At worst your waveform will
approach a pin shaped pulse, i.e. the wave is barely audible.
Contained within the wave reservoir are many useful pulse
waves, with wave ratios varying between 25% (TP008) and
10%(TP009). The latter is often used to emulate the sound
of a clavinet.
Another typical tool in analogue synthesis is the oscillator
synchronisation (or oscillator sync), originally devised to
avoid the inevitable drift between two VCOs. This method
opens the doors to the delectable ‘sync sounds’, two exam-
ples of which exist as ROM samples in the CS1x’s memory
(TP010/011).
The VCO Waveforms:
Sawtooth, Square, Pulse
Particular attention should also be paid to the Sine Wave.
This purely electronically generated wave is alone in not
having any harmonics at all, and as such is practically use-
less for subtractive synthesis. Nevertheless, the sine wave
can be found in many a synthesizer’s VCO section, and is
therefore also included in our Tutorial Bank (TP012). Just
how this wave can be used is fully explored in section “Pull-
ing out all the Stops
”. Much more common is the Noise Gen-
erator, a further source of sound apart from the VCOs. In the
era of digital synthesis, the poor old noise generator has
taken somewhat of a back seat. Nevertheless, noise genera-
tion still has many interesting applications.
The Filters –
Tastebuds for your Ears
Let’s take a look at subtractive synthesis’ most important
element, the Filter, or VCF (Voltage Controlled Filter). This
sound component removes selected frequencies from your
source material, i.e. the harmonically rich VCO waveforms.
The most common used type of filter is the low-pass filter,
which also helps the CS1x to its characteristic sound. Tech-
nically, the filter removes the upper frequencies selected by
it’s programmable cutoff point, whilst the lower frequencies
beyond this point pass through unaffected. Specifically, the
CS1x filter implementation revolves around a version of a
low-pass filter with a 12db/Oct rolloff. This means that fre-
quencies will be attenuated by 2kHz at 12dB, 4kHz at 24dB,
and so on, and as such is suitable for most applications.
The filter also has a Resonance Parameter, which accen-
tuates the frequencies near the cutoff-point. Resonance has
many applications beyond the typical character it lends to
many synthesizer sounds. Heavy use of resonance, coupled
with the above mentioned noise generator can result in many
attention-grabbing sounds. On the other hand, a gentle dose
of resonance can cleverly be used to ‘thin out’ a sound in a
way not possible by simply reducing its volume. In fact, it is
generally true that increasing the resonance a filtered signal
will make it sound quieter. Pay particular attention to your
sound’s bass region; it’s here where filtering can affect the
perceived ‘stability’ of your sound. Of course you may also
use resonance with the filter wide open. The following exam-
ple will illustrate how and when resonance may be used on
its own like this.
PERIMENT:
Select the harmonically rich choir sound (TP014). In the
context of a rhythm heavy dance arrangement, the choir
sound would benefit from a little more ‘transparency’. But
how? The filter frequency is already optimal, whilst you have
other plans for the effects. The solution here is a little trick:
use the resonance as a kind of ‘pseudo enhancer’, a psycho-
acoustic studio tool used to add high frequencies to ‘dull’
audio signals. Turn up your resonance! You will find your
sound has become ‘fresher’, and will now sit better in your
arrangement. Of course this trick can be used in other situa-
tions, for example to add a glossy sheen to dull bass drums,
tom samples and cymbals.
Exactly how Cutoff and Resonance will affect your sound is
easily revealed – simply play with the CS1x’s equally labelled
Knobs. Both parameters are fundamental in the creation of
sound, and their ability to give shape to sound are immense.
The low-pass filter’s abilities range from the simple ‘darken-
ing’ of a sound right through to fiddly tasks. One of these is
the creation of Formants. This, in simple terms, is the use of
resonance to accentuate a specific frequency range, so that
all partial tones in this region regardless of their fundamental
root frequency are noticeably pronounced. The vowels found
in human language (A-E-I-O-U) rely on characteristic for-
mant areas. To clarify all this, take the sound (TP015). Here
the two VCOs used are filtered differently, the first without
any resonance. The second however uses heavy resonance
to produce typical formants, which can be changed using
varying cutoff settings.
Dynamic Helpers –
Envelopes
All the sound components we have looked at so far have
been ‘static’ in their effect, that is to say that they haven’t
affected a sound differently over time. Enter the Envelope
Generators of the CS1x. Envelope generators control Volume
(AEG), the Filter (FEG) or the Pitch of your sound (PEG). An
envelope follows the traditional ADSR model: Attack con-
trols your sound’s fade-in time, Decay determines the time it
takes to reach the Sustain level, Sustain controls the volume
your sound will settle at whilst holding down a key, and
finally Release sets how long your sound will ring out after
releasing the key. Uniquely, the pitch envelope adds Intensity
and Level parameters to the standard envelope model (PEG
Init, Attack and Release Level) – see section “Performance
Mode
”, “Layer Edit3” in the manual.
Lets start with the Filter Envelope. It is responsible for
varying the filter’s cutoff point over time, and, as mentioned
above, crucial in determining the contour of your sound.
More often than not, envelopes with slow fade-out times are
used. This is achieved by dropping the filter’s cutoff point to
the programmed FEG Sustain Level. In our example sound
(TP016) this ‘dropping’ happens quite quickly. This is just
perfect for bass or sequencer sounds, which need to be
‘tight’. As a rule you should pay a lot of attention to your
envelopes – especially within song arrangements. You will
find that the decay times used have to ‘gel’ with the rhythmic
structure of a piece – a tricky piece of engineering, which
sadly is often overlooked. For example, a bass sound that
