Access Virus Rack User Manual page 37

Now modify the amplifier envelope so
you are working with a less grating
sound, but hold back on any other filter
or saturation modifications so you can
hear the purest oscillator signal possible.
Locate the section labeled "1", it is bor-
dered off in a separate area at the far
left of the section labeled OSCILLATORS.
No check out the two encoders labeled
SHAPE and WAVE SEL/PW. These enable
you determine the waveshape and con-
sequently the tonal spectrum of Oscilla-
tor 1.
In the sound program, SHAPE is preset to
the center position. The display shows
"Saw" for the sawtooth waveform.
Press and hold a key and slowly turn the
encoder clockwise. You should be able to
hear how the tone becomes increasingly
more hollow-sounding. You might say
this effect thins the sound out, but in
any case, the entire tonal spectrum is
affected by an equal measure, which is
an audio result filters are unable to
achieve.
The waveshape that is audible when you
turn the SHAPE encoder to the far right
is a so-called pulse wave. It is unique
because the duration of the negative
pulse is equal to the duration of the pos-
itive pulse: It has a so-called pulse width
of 50%. The tone of a pulse wave is dif-
ferent to that of a sawtooth wave
because it does not contain all overtones
in the natural overtone scale, only the
odd-numbered tones, i.e. the first (the
root note that determines the pitch),
third, fifth, and so forth. By turning the
SHAPE encoder from the sawtooth con-
trol range towards the pulse control
range, you are actually dialing every
other overtone out of the mix, which
explains why the sound becomes thinner.
You can continue modifying the sound
by reducing the symmetrical width of
the pulse wave. In the Virus, you can exe-
cute this sound-shaping measure via the
WAVE SEL/PW (PW = pulse width)
encoder, PROVIDED THE SHAPE PARAM-
ETER IS SET TO A POSITION IN THE NEGA-
TIVE HALF (RIGHT) OF ITS CONTROL
RANGE.
Rotate the WAVE SEL/PW encoder slowly
from the left to the right and leave the
SHAPE encoder at the far right position.
You can hear how the treble content of
the sound increases while the sound
becomes ever thinner. At the far right
position, the signal is no longer audible
because the pulse width is equivalent to
0% and consequently the wave no
longer oscillates.
Starting at the center position (12
o'clock) indicated by the sawtooth, turn
the SHAPE encoder counter-clockwise
towards the left. You can hear how the
overtones are increasingly mixed out of
the signal until you can only hear the
root note. This sound is produced by a
so-called sine wave, one of 64 other
waveshapes that you have at your dis-
posal for sound generation purposes.
These waveshapes can also be activated
via WAVE SEL/PW (WAVE SEL: Wave
Select), PROVIDED THE SHAPE PARAME-
TER IS SET TO A POSITIVE HALF (LEFT) OF
ITS CONTROL RANGE (EARLIER THAN 12
ACCESS VIRUS RACK 35
The First Oscillator