Access Virus Rack XL User manual

ENGLISH VERSION

©1997-2002 Access Music GmbH, Germany.
This manual, as well as the software and hard-
ware described in it, is furnished under licence
and may be used or copied only in accordance
with the terms of such licence. The content of
this manual is furnished for informational use
only, is subject to change without notice, and
should not be construed as a commitment by
Access Music GmbH. Access Music GmbH as-
sumes no responsibility of liability of any errors
or inaccuracies that may appear in this book.
Except as permitted by such licence, no parts
of this publication may be reproduced, stored in
a retrieval system, or transmitted, in any form or
by any means, electronic, mechanical, record-
ing, or otherwise, without the prior written per-
mission of Access Music GmbH.
VIRUS is a trademark of Access Music GmbH.
All other trademarks contained herein are the
property of their respective owners. All features
and specifications subject to change without
notice.
Written by Christoph Kemper, Uwe G. Hönig,
Wiland Samolak and Marc Schlaile.
Translation by Thomas Green and Howard
Scarr.
http://www.access-music.de
[email protected]

4
CHAPTER 2
Content
Content
IMPORTANT SAFETY REMARKS .............................. 8
PROLOGUE
INTRODUCTION
THE VIRUS ........................................................... 16
The Amplifier Envelope ........................................ 18
The First Filter...................................................... 20
Filter Modulation .................................................. 21
The Saturation Stage ........................................... 23
The Second Filter................................................. 23
Filter Routing ....................................................... 25
The First Oscillator ............................................... 27
The Second Oscillator .......................................... 28
The Mixer Section ................................................ 30
The LFOs ............................................................. 30
Soft Knob 1/2....................................................... 33
Volume and panorama ......................................... 33
Velocity................................................................ 34
Unison Mode........................................................ 34
The Effects........................................................... 35
The Arpeggiator ................................................... 37
SoundDiver Virus ................................................. 37
More to Come ...................................................... 38
CONCEPT AND OPERATION
Operating Modes ................................................. 40
OPERATION.......................................................... 43
All About The Memory.......................................... 46
Random Patch Generator ..................................... 47
Modmatrix And Soft Knobs................................... 49
Master Clock And Midi-Clock................................50
The Effects Section...............................................51
Audio Inputs ......................................................... 51
Audio Routing.......................................................53
Sound Categories ................................................. 53
Additional Functions .............................................54
THE PARAMETERS
OSC SECTION (ENCODER) .....................................58
Oscillator 1........................................................... 58
Oscillator 2........................................................... 58
Oscillator 3........................................................... 59
Sub Oscillator....................................................... 60
OSC SEKTION (MENU)...........................................61
Oscillator 1........................................................... 61
Oscillator 2........................................................... 61
Oscillator 3........................................................... 63
Oscillators ............................................................64
Ringmodulator......................................................64
Noise.................................................................... 65
FILTER SECTION (ENCODER) .................................66
FILTER SECTION/MENU.........................................67
Filter 1.................................................................. 67
Filter 2.................................................................. 68
Filters...................................................................68
ENVELOPE SECTION (ENCODER) ...........................72
Filter Envelope......................................................72
Amplifier Envelope................................................72
LFO SECTION (ENCODER) .....................................74
LFO 1 ................................................................... 74
LFO 2 ................................................................... 75
LFO 3 ................................................................... 75
LFO SECTION (MENU) ...........................................77
LFO 1 ................................................................... 77
LFO 2 ................................................................... 78
LFO 3 ................................................................... 80
EFX SECTION (ENCODER)......................................82
Reverb .................................................................82
Delay.................................................................... 84
Chorus .................................................................85

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Input .................................................................... 85
Analog Boost........................................................ 87
EFX SECTION/MENU ............................................. 88
Delay/Reverb ....................................................... 88
Distortion ............................................................. 91
Phaser ................................................................. 92
Chorus................................................................. 93
Equalizer.............................................................. 94
Vocoder ............................................................... 94
EDIT SECTION/ENCODER ...................................... 98
EDIT SECTION/MENU............................................ 99
Clock Tempo........................................................ 99
Common.............................................................. 99
Unison ............................................................... 102
Punch ................................................................ 103
Assign/Mod Matrix ............................................. 103
Velocity.............................................................. 106
ARPEGGIATOR&CTRL SECTION (ENCODER) ....... 108
ARPG&CTRL SECTION (MENU)............................ 110
Arpeggiator........................................................ 110
Categories ......................................................... 111
Second Output/Surround.................................... 111
THE MULTI MODE PARAMETERS
MULTIMODE PARAMETERS ................................ 114
THE GLOBAL PARAMETERS
GLOBAL PARAMETERS/ SYSTEM SECTION ......... 120
Random Patch Generator ................................... 120
Input (Global) ..................................................... 120
MIDI................................................................... 122
System .............................................................. 125
THE VOCODER
Vocoder ............................................................. 130
The parameters of the Virus vocoder ..................131
Notes about the vocoder.....................................132
THE VIRUS AND SEQUENCERS
Parameter Control via MIDI .................................136
Organizational Information..................................136
Handling MIDI Parameter Control........................137
Notes on Adaptive Parameter Smoothing ............138
Problems Related to Parameter Control ..............139
Dump - The Sound in the Song...........................140
TIPS, TRICKS& WORDS OF WISDOM
TIPS AND TRICKS ...............................................144
All abouts Inputs................................................. 145
About Effects......................................................145
Oscillators ..........................................................146
Filters.................................................................147
Saturation for Added Grit and Dirt .......................147
LFOs ..................................................................148
Volume Control...................................................150
Assign and the Soft Knobs.................................. 150
Arpeggiator ........................................................151
How to modulate the Vocoder parameters ..........151
MIDI ...................................................................152
The Operating System (OS).................................153
APPENDIX
SYSTEM EXCLUSIVE DATA .................................158
System Exclusive Implementation.......................158
Parameter Descriptions ......................................162
Multi Dump Table ...............................................174
Classes ..............................................................177
Mod Matrix Sources ..........................................179
Mod Matrix Destinations..................................... 180
Soft Knob Destinations ......................................181

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CHAPTER 2
Content
MIDI Implementation Chart................................. 182
FCC Information (U.S.A)...................................... 184
FCC Information (CANADA) ................................. 184
Other Standards (Rest of World) ......................... 185
Declaration of Conformity................................... 186
Warranty............................................................ 187
Many thanks to .................................................. 187
INDEX
INDEX ................................................................ 190

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8
CHAPTER 3
Important Safety
Remarks
PLEASE READ AND HEED THE FOLLOWING
SAFETY GUIDELINES!
A few fundamental rules on handling electrical
devices follow.
Please read all notes carefully before you power
the device up.
SET-UP
 Operate and store the device in enclosed
rooms only.
 Never expose the device to a damp environ-
ment.
 Never operate or store the device in extreme-
ly dusty or dirty environments.
 Assure that air can circulate freely on all sides
of the device, especially when you mount it to a
rack.
 Don’t set the device in the immediate vicinity
of heat sources such as radiators.

Don’t expose the device to direct sunlight.
 Don’t expose the device to strong vibrations
and mechanical shocks.
CONNECTIONS
 Be sure to use exclusively the included mains
power supply adapter.
 Plug the device only into mains sockets that
are properly grounded in compliance with statu-
tory regulations.

Never modify the included power cord. If its
plug does not fit the sockets you have available,
take it to a qualified electrician.
 Always pull the power plug out of the mains
socket when you won’t be using the device for
prolonged periods.
 Never touch the mains plug with wet hands.
 Always pull the actual plug, never the cord,
when you’re unplugging the device.
OPERATION
 Don’t set beverages or any other receptacle
containing liquids on the device.
 Make sure the device is placed on a solid
base. Set it on a stable tabletop or mount it to a
rack.

Make sure that no foreign objects fall into or
somehow end up inside the device’s housing.
In the event that this should occur, switch the
device off and pull the power plug. Then get in
touch with an authorized dealer.

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 Used on its own and in conjunction with
amps, loudspeakers or headphones, this device
is able to generate levels that can lead to irre-
versible hearing damage. For this reason, al-
ways operate it at a reasonable volume level.
MEMORY BATTERY CHANGE
The Virus stores its sound programs in a bat-
tery-buffered RAM. This battery (general type
designation: CR2032) should be replaced every
three to four years. The housing has to be
opened to change the battery, so take the de-
vice to a qualified service technician. Do your
part in protecting our environment and take it to
a shop that disposes of batteries properly.
Before you have the battery changed, save the
entire memory content of the RAM by loading it
to a sequencer via "Total Dump". Be advised
that RAM content is lost when the battery is
swapped. [“Midi Dump TX” on page 122]
CARE
 Do not open the device, it is not equipped
with any user-serviceable parts. Repair and
maintenance may only be carried out by quali-
fied specialists.
 Use only a dry, soft cloth or brush to clean the
device.

Do not use alcohol, solvents or similar chemi-
cals. These can damage the surface of the
housing.
FITNESS FOR PURPOSE
This device is designed exclusively to generate
low-frequency audio signals for sound engi-
neering-related purposes.
Any other use is not permitted and automatical-
ly invalidates the warranty extended by Access
Music Electronics GmbH.

10
CHAPTER 3

Prologue

12
CHAPTER 4
Prologue
Dear Virus Owner,
Congratulations on your choice, the new Virus.
You have purchased a cutting-edge synthesizer
that comes fully loaded with several revolution-
ary features. Here are just a few of the high-
lights:
The Virus delivers the sound characteristics and
tone of traditional analog synthesizers - for in-
stance the Prophet 5 or Memorymoog to name
just two popular examples of the species - in a
previously unparalleled level of quality and han-
dling ease. We’re not kidding, the Virus actual
delivers the authentic response of an analog
synth via a digital signal processor, although the
sound shaping and voicing options out-perform
those of it historical predecessors by a consid-
erable margin.
The Virus comes with 1024 slots for storing
SINGLE sounds. These are organized in four
banks. The first two banks (A and B) are located
in the RAM, so you can overwrite them with
new sounds. The other two banks are ”hard-
wired”, i.e. they’re programmed into the FLASH
ROM.
The Virus rack XL offers a maximum of 32 voic-
es. In Multi Mode, these are allocated dynami-
cally to 16 simultaneously available sounds.
You have up to three audio oscillators plus one
suboscillator, a noise generator, a ring modula-
tor, two Multi Mode filters, two envelopes, a
stereo VCA, three LFOs and a saturation stage
(SATURATOR) for cascade filtering, tube and
distortion effects.
The Virus offers a veritable number of effects.
You have a powerful Chorus/Flanger section at
your disposal, as well as the Analog Boost - a
controllable bass emphasis, with each effect
available separately for every sound. Further-
more there is a 6-stage Phaser, and a patch
Distortion. You also get a global reverb/delay
unit that lets you create high-quality reverb ef-
fects and rhythmic delay taps. Delay time can
be synced up to MIDI clock.
With the benefit of two external audio inputs,
the Virus may also serve as an FX device and
signal processor that you can use creatively to
come up with all kinds of effects. External sig-
nals can be processed with filter, gate and lo-fi
effects, routed to the Virus effects section and
serve as a modulation source for frequency and
ring modulation.
Beyond that, you can use internal or external
signals as sources for the Virus’ on-board voco-
der serve. The vocoder works with up to 32 fil-
ter bands and offers diverse manipulation and
modulation options.
You'll find parallel external audio inputs on the
front and back panel. You can determine the in-
put sensitivity via a gain selector switch. You're
also free to activate a special Phono EQ that
enables you to connect a record player via a
suitable cord.
The up to three main oscillators produce 66
waveshapes, three of which are dynamically
mixable so that spectral effects are possible
within the confines of a single oscillator. In con-
ventional synthesizers, this type of effect re-
quires several oscillators. Synchronization,
frequency modulation and ring modulation be-
tween the audio oscillators delivers additional
complex spectral effects that you can use for all
kinds of sound shaping purposes.
The filters can be switched in series or in paral-
lel within the voices via several options. When
you switch the filters in series, the saturation
stage is embedded between the filters. Conse-
quently, an overdriven filter resonance can be
re-filtered within the same voice! A maximum of
six filter poles (36 dB slope!) enables radical
tonal manipulations.

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The LFOs feature 6 continuous variable wave-
shapes each, including a triangle with variable
symmetry and infinitely variable aperiodic oscil-
lations for random variation of the controlled
parameters. The LFOs are capable of poly-
phonic as well as monophonic oscillation. In
other words, if several voices are active, the
LFOs can run independently or in sync. A
number of keyboard trigger options enable you
start LFO waveshapes with variable phase
lengths at the beginning of a note and/or to cy-
cle once only, like an envelope.
Next to the numerous ”hard-wired” or fixed
modulation configurations, you can assign six
modulation sources to up to nine different mod-
ulation destinations via the Modulation Matrix.
For your modulation sources, you have LFOs,
velocity, the pitch bender, aftertouch, the mod-
ulation wheel, numerous MIDI controllers and
other sources to chose from. For your modula-
tion destinations, you can select any sound pa-
rameter of the Virus that is conducive to being
remote controlled.
Up to 16 arpeggiators are available in MULTI
mode. These give you countless options for
creating arpeggios, which can also be synced
up to MIDI clock.
Sounds and effects are patched out via four au-
dio outputs which of course can also be used to
route two stereo signals out.
The Virus rack XL comes with a powerful soft-
ware editor for PC and Macintosh. It lets you
edit and manage sounds on a large-scale user
interface. You can access every sound parame-
ter of the Virus rack XL directly via mouse click.
When you edit a parameter, the Virus will render
the changes immediately in real time. Accord-
ingly, every parameter change that you make
using the encoder knobs (those knobs without
left and right control range limits) on the Virus
rack XL appears immediately on the screen. In-
cidentally, this editor is based on Emagic's pop-
ular SoundDiver.
In all modesty, we are especially proud of a fea-
ture we developed called Adaptive Parameter
Smoothing. For the first time in the history of
synthesizers equipped with memories, you can
manipulate a knob or control feature without an
audible step or increment. In other words, the
sound does not change abruptly but SEAM-
LESSLY. No more zipper noises! The Virus re-
sponds just as smoothly as analog synthesizers
did prior to the introduction of digital sound
storage.
And users of contemporary software sequenc-
ers will appreciate the fact that the Virus sends
all sound shaping commands immediately in
the form of MIDI Controller or Poly Pressure da-
ta (and of course accepts all of the correspond-
ing Controller and SysEx messages). This
feature lets you dynamically control the Virus
and all its functions via computer.
Although far from complete, the features listed
above give you some indication that you now
own an exceptionally versatile, high-quality mu-
sical instrument that will give you plenty of joy
for years to come. We certainly hope you can
fully exploit the enormous potential of this fine
instrument.
Have fun and enjoy!
Your Virus Development Team

14
CHAPTER 4
Prologue

Introduction

16
CHAPTER 5
Introduction
The Virus
This section provides deliberate, step-by-step
guidelines on operating and handling the Virus
for those of you who are new to the world of
synthesizers and MIDI. The following covers ba-
sics such as how to connect the Virus to an AC
power supply, your MIDI system and your audio
system. Then we will guide you through a series
of experiments designed to demonstrate the
different functional groups, their control fea-
tures and the tasks they execute.
After you have finished reading this section, you
will be able to handle virtually all of the sound
generating and sound shaping functions of the
Virus. All of these are described in context.
Even the majority of less significant functions,
accessible via menus, are discussed here. You
will find a detailed, comprehensive description
of all functions of your new synthesizer in the
section following this introduction.
Please keep in mind that within confines of this
introduction, we are unable to impart all of the
knowledge and skills in acoustics, sound syn-
thesis and MIDI control you might desire or
need to acquire. If you are keen to learn more
about these subjects, you should consider be-
coming a regular reader of one or several of the
leading trade publications in your country. Your
local musical instruments dealer or more expe-
rienced musicians will be able to recommend
the best magazines to you. And of course there
is a wide range of books available on these
subjects.
If you decide to read this section, we recom-
mend you read it in its entirety from the start -
rather than begin with a subsection that is of
particular interest to you. A fitting metaphor for
the basics discussed in this section might be a
house where each bit of information in a sub-
section is a brick that builds on a preceding
brick and interlocks with those next to it. You
want your knowledge base to be a sound struc-
ture so you won’t run into problems when you
find one of the “bricks” is missing.
CABLE CONNECTIONS
Before you connect the Virus to an AC outlet
and the rest of your equipment, ensure that all
of the devices are switched OFF. If your Virus
does not have a build-in keyboard, then con-
nect the MIDI OUT of the desired MIDI send de-
vice (keyboard, computer, hardware sequencer,
etc.) with the MIDI IN of the Virus.
Connect the audio outputs of the Virus with the
signal inputs of your audio system. In order to
receive a signal, as a minimum you must con-
nect the output OUT 1 R/MONO. However, we
recommend you also connect the output OUT 1
L so you are able to enjoy the stereo sounds of
the Virus.
Once you have established the desired cable
connections, make sure the main volume con-
trols of all the connected devices are dialed to
the lowest possible setting. Switch the devices
on in the following sequence: the MIDI send de-
vice (computer, master keyboard, etc.) first,
then the sound generators (Virus and the other
signal sources), followed by the mixing console
and finally the amplifier.
POWER UP THE VIRUS RACK XL
Power up the Virus rack XL by pressing the
POWER button. To shut the device down, press
and hold this button for approx. two seconds.
Now while you are sending notes on MIDI
Channel 1 of the Virus, turn the master volumes
of the connected devices up in the same order

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that you switched the devices on. Be sure to
keep on eye on the signal level indicators of
your mixing console.
LISTENING TO THE FACTORY
SOUNDS
The program memory of the Virus was loaded
with sound programs (SINGLE PROGRAMs)
and sound combinations (MULTI PROGRAMs)
before it left the factory. To hear the SINGLE
PROGRAMs (and gain an initial impression of
the possibilities your new instrument has to of-
fer in terms of sounds), first make sure your
MIDI source is sending on MIDI Channel 1.
Press the SINGLE button. A number, a letter,
number and name appear in the display. These
indicate the the MIDI Channel, the current Pro-
gram Bank (A to H) as well as the number and
name of the current sound program.
Now if you play notes you should be able to
hear this sound and a quarter note (the round
dot at the end of the note staff is solid black)
should appear in the display every time you
press a key and release a key. If you do not hear
a sound but you see a half note (blank note
head) check to see if you are sending on the
wrong MIDI Channel.
Press the VALUE button to call up the 128 sin-
gle programs of Bank A in sequence. (The VAL-
UE encoder is inactive in this operating mode.)
In order to hear the sound programs in banks B
to H, simply use the PARAMETER/BANK but-
tons to step from one program bank to another.
You’ll find that some sound programs are la-
beled with the abbreviations ”INP” or ”VOC”.
These use the external audio input as a signal
source for the filter section (INP) or vocoder
(VOC). This means that you won’t hear anything
until you route an audio signal into the external
audio inputs.
LISTENING TO THE MULTI PRO-
GRAMS
The Virus not only has the capability of playing
SINGLE PROGAMs, but also combinations
consisting of more than one sound simultane-
ously (MIDI Multi Mode). To call up the MULTI
PROGRAMs, press the MULTI button and se-
lect these combination programs via the VALUE
button. The Virus features “only” 128 MULTI
PROGRAMs, so you don’t have to switch back
and forth between banks they way you just did
while activating single programs.
The majority of available MULTI PROGRAMs
contain sound combinations that are controlled
via a single MIDI channel. In these MULTI PRO-
GRAMs, the sounds involved are allocated
side-by-side (split) or on top of one another
(layered) on the keyboard. In other MULTI PRO-
GRAMs, the sounds are divided up over several
MIDI channels to make it easier to work with a
sequencer. If you activate a MULTI PROGRAM
and hear a single sound only, then you can con-
trol this MULTI PROGRAM via several channels.

18
CHAPTER 5
Introduction
SOUND CATEGORIES
To help you find the type of SINGLE sound you
are looking for more quickly, the Virus operating
system lets you define so-called „categories“
and save this information together with each of
your SINGLE sounds.
Each SINGLE sound can „belong“ to two cate-
gories at the same time. Of course the catego-
ries of all the presets in Banks C to H are fixed,
but for sounds in the RAM Banks (A and B) they
can be defined and saved together with the
program.
To search for sounds in a specific category (in
SINGLE or MULTI-SINGLE mode):
Press and hold the SINGLE button. This causes
the currently selected category to appear in the
display, and it can be changed by stepping up
or down with the Parameter buttons. Having
found the category you want, do not release the
SINGLE button and scroll through the sounds
using the Value buttons. Release the SINGLE
button when you have found what you are loo-
king for. SINGLE sounds which do not belong
to the currently selected category are simply
skipped over.
YOUR FIRST SOUND PROGRAM
If you have never created or changed a sound
on a synthesizer, we now have the pleasure of
introducing you to this fascinating process.
Press the button
SINGLE and select the single
program “A127 - START -” by using the
VALUE
buttons. Press any key on the connected key-
board. You should hear a sound that, for lack of
better description, is a bit harsh or biting, but
above all completely static. It should start im-
mediately after you press a key and sustain in-
definitely for as long as you hold the key down.
As soon as you release the key, the sound
should end abruptly. This sound is not designed
to be especially pleasant; it is intended to be as
neutral as possible to give you a basis from
which you can begin creating or shaping your
own sound.
 THE AMPLIFIER ENVELOPE
Long-term exposure to this sound will definitely
grate on your nerves, so let’s get started with
changing it into a signal you might enjoy hea-
ring, beginning with the volume characteristics.
Locate the two vertically arrayed buttons next
to the seven LEDs. Use these UP and DOWN
buttons to select from among the seven para-
meter groups and/or sections. The appropriate
LED lights up to indicate that the given section
has been selected. Select the ENV section. The
labels on the five encoder knobs for this section
read ATTACK, DECAY, SUSTAIN, SUS TIME and
RELEASE.
These controls will help you to dial in volume
characteristics called an amplifier envelope and
put an end to the nerve-racking drone that may
remind you of one of those cheesy organs that
you hear in ‘60s B-movie sound tracks.
The section labeled ENV addresses the enve-
lope. On a synthesizer, an envelope is used to
modulate sound over time. The Virus has two
envelopes, one for volume (AMP ENV) and one
for the filters (FILT ENV), which we will learn mo-
re about later. The five encoder knobs serve to
shape either the amplifier envelope or the filter
envelope. Make sure that you can see AMP
ENV in the display, and not FILT ENV. If this is
not the case, use the PARAMETER buttons to
set the section to the amplifier envelope.

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Rotate the ATTACK encoder while you repea-
tedly engage a key to hear the note. The further
you turn the encoder up, the longer it takes for
the sound to achieve maximum volume after
the start of the note. So you can say ATTACK
controls the initial volume swell of the sound.
Take a look at the display of the Virus to gain an
impression of the difference between these two
values. It shows two numeric values when you
dial a encoder: at the left you can see the value
stored in the sound program and at the right,
the numeric equivalent to the value determined
by the current position of the encoder.
Now fiddle with the DECAY encoder while you
repeatedly press a key to activate a note. Hold
the key down for good while. You will notice
that the volume, once it reaches maximum level
at the end of the ATTACK phase, drops until it
reaches a minimum level. The DECAY encoder
determines the speed, or in synthesizer jargon,
the rate at which the volume decreases.
However, the DECAY level does not always
drop to the minimum level; you can determine a
random value between the maximum and mini-
mum levels at which the volume remains con-
stant. This level in turn is controlled via the
SUSTAIN encoder.
Whenever the SUSTAIN level is set to maxi-
mum, the volume cannot drop during the DE-
CAY phase; in other words, in this situation the
DECAY encoder is ineffective.

The individual functions of a synthesizer are
designed to interact; many functions are de-
pendent on other functions. In a number of ca-
ses this means that some functions are
subordinate to others, i.e. the effectiveness of a
control feature is altered, modified or even ne-
gated completely by other related functions.
The final encoder, 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 de-
pends 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 DECAY 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 next phase of the amplifier envelope is de-
termined by the SUSTAIN-TIME encoder: If the
encoder is set to the center position, then the
SUSTAIN level remains constant through to the
end of the note.
If you turn it counter-clockwise to the left, then
the level drops off at an increasing rate towards
the minimum level much in the manner you just
experienced with the DECAY encoder; If you
turn the encoder clockwise to the right, the level
rises at an increasing rate to maximum and
remains there until you release the key.
T he amplifier envelope can be described as a
variable curve which, depending on the type
and duration of attack, hold and release data,

20
CHAPTER 5
Introduction
automatically influences an imaginary volume
encoder (turns it up or down). At the beginning
of the note, ATTACK controls the rise or rate of
increase 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 ri-
se 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 encoders labeled ATTACK,
DECAY, TIME and RELEASE control a speed or
rate, where as SUSTAIN actually controls a le-
vel.
 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 dra-
stic 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.
Use the UP or DOWN buttons to activate the fil-
ter section FILT. The second encoder knob in
this row is labeled CUTOFF (not to be confused
with CUTOFF 2!). Rotate the encoder to the left
and right and note how the sound becomes
muddier and clearer in response to the direction
in which you turn the encoder. (To ensure this
effect and the following aural experiments are
most pronounced, adjust the amplifier envelope
so that the Virus generates a constant level whi-
le you hold a key down).
This is how a low pass filter works: it suppres-
ses, or in technical jargon, attenuates the higher
frequencies in a signal and allows the lower fre-
quencies through. Think of the CUTOFF enco-
der as a bouncer and the Virus as your pub. You
can tell it which frequencies to let in and which
frequencies to keep out. The frequencies above
the so-called cutoff or filter frequency are sup-
pressed, those below it remain unaffected.
Now we'll look at a parameter that is not assi-
gned a dedicated knob of its own, but can be
dialed up in the display. This type of parameter
may be selected via the PARAMETER buttons
and then adjusted with the VALUE knob or the
VALUE buttons.
Select the FILTER 1 Mode parameter via the
PARAMETER buttons. To do this, make sure
that the display is still in the filter section FILT.
This parameter enables you to select a filter
operating mode from the four available options:
- LOWPASS the low pass filter we have just
discussed.