The Lfos - Access VIRUS CLASSIC User Manual

The VIRUS' ring modulator is a new sound source. The output of the two oscillators is multiplied to
create interesting sounds with rich enharmonic overtones. These overtones are highly dependent
on the frequency coherence of both oscillators and it's waveforms. The frequency coherence can be
changed, for instance use the OSC2 SEMITONE parameter. To blend in the ring modulator use
EDIT: RINGMODULATOR VOLUME (in OSCILLATOR EDIT Menu). If the RINGMODULATOR VOL-
UME is zero, the ring modulator is switched off. OSC VOL does not affect the ring modulator level
(or indeed the noise volume). Therefore the original oscillator signal can be leveled independently of
the ring modulator. Be sure to check out what the ring modulator does when you select a sine wave
for Oscillator 1 and 2.
Now we can go on and solve the mysteries of the signal flow as determined by the FILTER ROUT-
ING operating mode SPLIT: Here Oscillator 1 and the SubOscillator are routed to Filter-1, whereas
Oscillator 2 and the Noise Generator are routed to Filter-2. Although the sound sources are split into
two signal paths, you can still control the volume levels of the different elements as well as OSC
VOL in the usual manner.

The LFOs

When you first started this series of experiments with sounds, we promised that many of the func-
tions the Virus can be "programmed" so that they are executed automatically. You have already
learned how to control the volume and cutoff frequencies of both filters as well as the pitch and
intensity of the frequency modulation of Oscillator 2 via "preprogrammed" envelopes. These
options are great, but you have already encountered a number of functions where it would be a
helpful if you could also program them to be executed automatically. And of course envelopes are
great modulation sources, but you have to play a note every time you want to initiate an envelope.
During your experiments you probably came across a function or two you would like to be able to
control periodically - independently of notes. Some features that come to mind are traditional tech-
niques such as vibrato (periodic pitch control) and tremolo (periodic volume control). Another option
you might like to have at your disposal is random parameter control.
In the Virus, both of these tasks are executed by a so-called LFO (low frequency oscillator) that
oscillates at frequencies below the audible range. An LFO is similar to the oscillators you have
encountered thus far, but it oscillates significantly slower so that its output signal is too low for
human hearing. So what good are they if you can't hear them? LFOs are used in much the same
manner as envelopes, with the major difference that the are repeated indefinitely.
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