Access virus indigo ii Manuale Utente

CHAPTER 4

Introduction

to others, i.e. the effectiveness of a control fea-
ture is altered, modified or even negated com-
pletely by other related functions.

The final pot, RELEASE, determines the speed
or rate at which the volume decreases when
you release the key: At low values the sound
ends relatively abruptly, at high values, the
sound fades out more gradually and softly. The
length of the RELEASE phase also depends on
which level the amplifier curve is at when you
release the key: The lower the level, the shorter
the RELEASE phase. If you dialed in a brief DE-
CAY or SUSTAIN-TIME phase and it ended
while you held the key down then of course
there will not be an audible RELEASE phase.

The amplifier envelope can be described as a
variable curve which, depending on the type
and duration of attack, hold and release data,
automatically influences an imaginary volume
pot (turns it up or down). At the beginning of the
note, ATTACK controls the rise or rate of in-
crease to the maximum level. Once the maxi-
mum level is achieved, DECAY determines the
fall or rate of decrease to the SUSTAIN value,
which is infinitely variable between the mini-
mum and maximum levels. The amplifier enve-
lope may remain at this value until the end of
the note, fall towards the minimum level as de-
termined by the variable TIME value, or even
rise again towards the maximum level. After the
end of the note, RELEASE controls the fall or
rate of decrease to the minimum level. Conse-
quently, the control pots labeled ATTACK, DE-
CAY, TIME and RELEASE control a speed or
rate, where as SUSTAIN actually controls a lev-
el.

THE FIRST FILTER

Now we will take a look at a component of a
synthesizer that is generally regarded as the
most important functional unit as it enables
drastic sound shaping measures: the filter - or
in the case of the VIRUS, the two filters.

But first we will concentrate on just one of the
two filters.

Locate the Cutoff pot (not to be confused with
Cutoff 2!) in the section labeled FILTERS, direct-
ly above the section labeled AMPLIFIER. Rotate
the pot to the left and right and note how the
sound becomes muddier and clearer in re-
sponse to the direction in which you turn the
pot. (To ensure this effect and the following au-
ral experiments are most pronounced, adjust
the amplifier envelope so that the VIRUS gener-
ates a constant level while you hold a key
down).

This is how a low pass filter works: it suppress-
es, or in technical jargon, attenuates the higher
frequencies in a signal and allows the lower fre-
quencies through. Think of the Cutoff pot as a
bouncer and the VIRUS as your pub. You can
tell it which frequencies to let in and which fre-
quencies to keep out. The frequencies above
the so-called cutoff or filter frequency are sup-
pressed, those below it remain unaffected.

-100%

100%

1+2

FILTER BALANCE

CUTOFF

RESONANCE

ENV AMOUNT

CUTOFF 2

SELECT

MODE

FILT 1

FILT 2

EDIT

FILT 2

FILT 1

FILTERS