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Program P4: Oscillators & Filters 4-1: Oscillators & Filters
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Program P4: Oscillators & Filters
4-1: Oscillators & Filters
4-1a: Oscillators
VOLTAGE CONTROLLED OSCILLATOR 1
WAVE FORM [ , , , ]
This sets the basic timbre of Oscillator 1.
(Triangle Wave): This is a very basic waveform
with few harmonics and a soft, rounded tone color.
You can create a sine wave by processing the Triangle
Wave through the Lowpass Filter. The original MS-20
manual notes that Triangle waves are “excellent for
flute, vibes and other such effects.”
Note: The Triangle is a little more computationally
intensive than the other waveforms, so using it will
result in slightly lower polyphony.
(Sawtooth): This is the foundation of the
traditional, buzzy analog synth sound. The original
MS-20 manual describes it this way: “A waveform rich
in all the harmonics, and one of the most useful to the
synthesist. Used for string, brass, voice and other
harmonically rich sounds.”
(Square/Pulse Wave): This is a variable
waveform shape, whose timbre depends upon the PW
setting, as described below.
(White Noise): This is an un-pitched sound,
containing equal amounts of all frequencies. The
original MS-20 manual suggests using this for “wind,
surf, gunshot, percussion, and other such effects.”
PW [0.00…10.00 (50%…0%)]
This adjusts the pulse width when Oscillator 1’s
Waveform is set to Square/Pulse.
0.00 produces a square wave. Increasing the value
produces narrower pulses, until at 10.00 the pulse is so
narrow as to be silent.
The original MS-20 didn’t support pulse-width
modulation, except by sweeping the knob manually.
With the MS-20EX, however, you can modulate PW via
AMS. Try using a medium-speed triangle LFO, or a
sweeping EG.
More on Pulse Width
Pulse waveforms are simple, rectangular shapes. The
Pulse Width sets the percentage of the waveform spent
in the “up” position. A few examples are shown in the
diagram below. Note that a square wave is just a pulse
wave with PW/PWM set to 0.00.
The width controls the timbre of the oscillator, from
pure and hollow at 0.00 (a square wave) to thin, reedy,
and nasal at higher settings.
At the maximum setting of 10.00, the Pulse wave will
be silent, since this eliminates the “pulse” altogether.
4–1a
4–1
f
4–1PMC4–1b 4–1c 4–1d 4–1e
Pulse Width = 0.00
Pulse Width = 9.00
Pulse Width = 5.00