Access Virus B, Virus A User Manual
©2000 Access Music GmbH, Germany. 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.
Graphic Design and DTP by
Babylonwaves Media.
http://www.access-music.de
info@access-music.de
CONTENT
INTRODUCTION - 15
The Virus ..................................................16
The Amplifier Envelope .......................20
The First Filter .........................................23
Filter Modulation ...................................25
The Saturation Stage ............................27
The Second Filter................................... 28
Filter Routing ..........................................32
The First Oscillator................................ 34
The Second Oscillator ...........................37
The MIXER Section................................ 39
The LFOs ...................................................41
LFO 2 ......................................................... 46
Velocity.................................................... 48
Unison Mode..........................................49
The Chorus/Flanger Effect.................. 50
The Delay Effect...................................... 51
More to Come .........................................52
CONCEPT AND OPERATION - 53
Operating Modes.................................. 54
The Multi-Single Mode.........................55
Edit Buffers ..............................................57
HANDLING - 59
Parameter Selection and
Data Entry...............................................60
Knob Modes ........................................... 63
Display of values ................................... 64
ALL ABOUT THE MEMORY - 67
Store ......................................................... 68
Compare..................................................69
MASTER CLOCK & MIDI-CLOCK - 71
Master Clock and Midi-Clock .............. 72
THE MODULATION MATRIX AND
DEFINABLE KNOB - 75
Creating Modulation Configurations
via Assign................................................ 76
The Definable Knobs.............................78
THE EFFECTS SECTION - 81
The Effect Section ................................. 82
AUDIO INPUTS - 83
Audio Inputs........................................... 84
OSC Volume / Input.............................. 85
Input Level Indicator ............................86
INTERNAL AUDIO ROUTING - 87
Aux Buses................................................88
The Audio Outputs ...............................89
ADDITIONAL FUNCTIONS - 91
Panic Function ....................................... 92
Audition function.................................. 92
Reset Function .......................................92
THE PARAMETERS - 93
Sound Parameters with a Dedicated
Control Element ....................................94
LFO 1 – Panel ...........................................95
LFO 1 – EDIT Menu................................. 97
LFO 2 - Panel .........................................100
LFO 2 Edit-Menu ................................... 101
LFO 3 ........................................................102
OSCILLATOR 1- Front Panel................ 104
Oscillator 2 – front Panel....................105
OSCILLATOR – EDIT-Menu................ 106
Menu parameters for Oscillator-2...107
Menu-Parameter for Oscillator-3... 109
Menu-Parameters of the
Suboscillator ...........................................111
Mixer-Parameters within then
Oscillator-edit-Menu ...........................112
Mixer........................................................ 113
Filters – Panel.........................................114
Filter-Edit-Menu....................................118
Amplifier ................................................ 122
Main Edit Menu (Common)............... 123
Assign......................................................129
Velocity................................................... 133
WITHIN THE CTRL-MENU - 135
COMMON ..............................................136
ARPEGGIATOR....................................... 137
DEFINABLE 1 / DEFINABLE 2 .............. 140
MULTI MODE parameters..................142
PARAMETER OF THE FX-MENU- 149
The internal Effects .............................150
Input........................................................150
Follower (Envelope-Follower)........... 154
Ringmodulator ..................................... 155
Vocoder ..................................................156
Distortion............................................... 157
Analog Boost.........................................158
Phaser .....................................................159
Chorus..................................................... 161
Delay/Reverb.........................................162
GLOBAL-, MIDI- AND SYSTEM
PARAMETERS - 173
Global Parameters............................... 174
System ................................................... 180
RANDOM PATCH GENERATOR - 183
Random Patches...................................184
CATEGORIES - 187
Sound Categories.................................188
THE KEYBOARD VERSIONS OF
THE VIRUS - 189
The Virus kb and the Virus Indigo... 190
Local off and “Three in One”............ 190
Keyboard & Company.........................192
The Keyboard-Modes..........................195
THE VOCODER OF THE VIRUS - 201
Vocoder ................................................. 202
The parameters of the vocoder.......204
Notes about the vocoder ...................210
THE VIRUS AND SEQUENCERS - 213
Parameter Control via MIDI ..............214
Organizational Information.............. 214
Handling MIDI Parameter Control ..216
Notes on Adaptive Parameter
Smoothing............................................. 217
Problems Related to Parameter
Control.................................................... 221
DUMP: The Sound in the Song .........222
TIPS, TRICKS AND OTHER WORDS
OF WISDOM - 227
MULTI SINGLE Mode .......................... 228
Value Buttons ......................................229
All abouts Inputs................................. 229
About the Delay/Reverb..................... 231
The Virus as an Effect Device............232
Envelope Follower ...............................233
Oscillators ............................................. 234
Filters.......................................................237
SATURATION for Added Dirt ............239
LFOs ........................................................240
Volume Control ...................................242
ASSIGN and the DEFINABLE Knobs. 243
ARPEGGIATOR...................................... 244
MIDI........................................................ 245
PRIORITY................................................ 247
Installing an operating system
update.................................................... 247
Loading the Operating System from
One Virus to Another ......................... 249
Software Updates............................... 250
APPENDIX - 251
System Exclusive Data........................252
Parameters Describtion..................... 258
Multi Dump Table................................273
Classes ................................................... 276
Mod Matrix Sources ..........................280
Mod Matrix Destinations...................281
Definable Knobs Destinations ........ 282
MIDI Implementation Chart.............284
FCC Information (U.S.A).....................286
FCC Information (CANADA).............. 288
Other Standards (Rest of World).....289
Declaration of Conformity................290
Garantie Bestimmung....................... 292
Warranty ............................................... 293
6
Important Safety Remarks
ACCESS VIRUS OS4
7
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 environment.
Never operate or store the device
in extremely 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 statutory 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.
CHAPTER
8
Safety Remarks
2
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.
Memory battery change
The Virus stores its sound programs in a battery-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 device 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 (see
“Midi Dump TX” on page 174).
Used on its own and in conjunc-
tion with amps, loudspeakers or
headphones, this device is able to
generate levels that can lead to
irreversible hearing damage. For
this reason, always operate it at a
reasonable volume level.
Care
Do not open the device, it is not
equipped with any user-serviceable parts. Repair and maintenance may only be carried out by
qualified specialists.
Use only a dry, soft cloth or brush
to clean the device.
Do not use alcohol, solvents or
similar chemicals. These can damage the surface of the housing.
Fitness for Purpose
This device is designed exclusively
to generate low-frequency audio
signals for sound engineeringrelated purposes. Any other use is
not permitted and automatically
invalidates the warranty extended
by Access Music Electronics GmbH.
ACCESS VIRUS OS4
9
CHAPTER
10
Safety Remarks
2
Prologue
ACCESS VIRUS OS4
11
Dear Virus Owner,
Congratulations on your choice,
the new Virus. You have purchased
a cutting-edge synthesizer that
comes fully loaded with several
revolutionary features. Here are
just a few of the highlights:
The Virus delivers the sound characteristics and tone of traditional
analog synthesizers - for instance
the Prophet 5 or Memorymoog to
name just two popular examples
of the species - in a previously
unparalleled level of quality and
handling ease. We’re not kidding,
the Virus actual delivers the
authentic response of an analog
synth via a digital signal processor
chip, although the sound shaping
and voicing options out-perform
those of it historical predecessors
by a considerable margin.
The Virus comes with 512 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 offers a maximum of 24
voices. In Multi Mode, these are
allocated dynamically to sixteen
simultaneously available sounds.
You have no less than three audio
oscillators plus one suboscillator, a
noise generator, a ring modulator,
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 arsenal
of effects. You have seven powerful
sound-sculpting functions, including chorus, phaser and distortion,
at your disposal, with each effect
available separately for every
sound. Thus, in 16-way MULTI
mode, the Virus offers 80 effects,
no less!. You also get a global
reverb/delay unit that lets you create high-quality reverb effects and
rhythmic delay taps. Delay time
can be synced up to MIDI clock.
12
CHAPTER
Prologue
3
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 signals 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 vocoder serve.
The vocoder works with up to 32
filter bands and offers diverse
manipulation and modulation
options.
The 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
conventional synthesizers, this
type of effect requires several oscillators. Synchronization, frequency
modulation and ring modulation
between 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 parallel within the
voices via several options. When
you switch the filters in series, the
saturation stage is embedded
between the filters. Consequently,
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.
The LFOs feature 68 continuous
variable waveshapes each, including a triangle with variable symmetry and infinitely variable
aperiodic oscillations for random
variation of the controlled parameters. The LFOs are capable of polyphonic 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 cycle once only, like an envelope.
Next to the numerous ”hardwired” or fixed modulation configurations, you can assign three
modulation sources to up to six
different modulation destinations
ACCESS VIRUS OS4
13
via the Modulation Matrix. For
your modulation sources, you have
LFOs, velocity, the pitch bender,
aftertouch, the modulation wheel,
numerous MIDI controllers and
other sources to chose from. For
your modulation destinations, you
can select any sound parameter 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 six audio outputs which of
course can also be used to route
three stereo signals out.
In additional to its killer sounds
and tone, the Virus was designed
to deliver ultimate handling and
control comfort. It is equipped
with dedicated knobs and buttons
for the crucial synthesizer functions, further parameters are
accessible via data entry procedures. We distinguished between
these two levels of expertise to
enable you to create complex
sounds while keeping the user
interface as clear and uncluttered
as possible.
In all modesty, we are especially
proud of a feature 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 SEAMLESSLY. No more zipper
noises! The Virus responds just as
smoothly as analog synthesizers
did prior to the introduction of digital sound storage
And users of contemporary software sequencers will appreciate
the fact that the Virus sends all
sound shaping commands immediately in the form of MIDI Controller or Poly Pressure data (and of
course accepts all of the corresponding Controller and SysEx
messages). This feature lets you
dynamically control the Virus and
all its functions via computer.
14
CHAPTER
Prologue
3
Although far from complete, the
features listed above give you
some indication that you now own
an exceptionally versatile, highquality musical 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
By the way: a rack mounting kit is
optionally available for the Virus b.
Feel free to get in touch with your
local authorized dealer for more
info.
Many thanks to:
Ben Crosland, Thomas Green, Axel
Hartmann, Uwe G. Hönig, Jörg
Hüttner, Oliver Käser, Andrea
Mason, Thorsten Matuschowski,
Paul Nagle, Kai Niggemann, Rob
Papen, Wieland Samolak, Howard
Scarr, Hans-Jörg Scheffler, Jenny
Simon, Matt Skags, Joeri Vankeirsbilck, Jay Vaughan, Jens Wegerhoff
and Daniel Wewer.
Introduction
CHAPTER
16
Introduction
4
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 basics 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 features and
the tasks they execute.
Please keep in mind that within
confines of this introduction, we
are unable to impart all of the
knowledge and skills in acoustics,
sound synthesis and MIDI control
you might desire or need to
acquire. If you are keen to learn
more about these subjects, you
should consider becoming a regular reader of one or several of the
leading trade publications in your
country. Your local musical instruments dealer or more experienced
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.
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, along
with their control features. 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.
If you decide to read this section,
we recommend 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 subsection 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 structure so you won’t
run into problems when you find
one of the “bricks” is missing.
ACCESS VIRUS OS4
The Virus
17
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 connect the MIDI OUT
of the desired MIDI send device
(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
connect 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 controls of
all the connected devices (Virus:
MASTER VOLUME, located at the
upper left hand of the control
panel) are dialed to the lowest possible setting. Switch the devices on
in the following sequence: the
MIDI send device (computer, master keyboard, etc.) first, then the
sound generators (Virus and the
other signal sources), followed by
the mixing console and finally the
amplifier.
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 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
offer 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 indi-
CHAPTER
18
Introduction
4
cate the the MIDI Channel, the current Program Bank (A to D) 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 ≤ 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 single programs of Bank A
in sequence. (The VALUE pot is
inactive in this operating mode.) In
order to hear the sound programs
in banks B, C and D, simply use the
PARAMETER/BANK buttons to step
from one program bank to
another.
You’ll find that some sound programs are labeled 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 Programs
The Virus not only has the capability of playing SINGLE PROGAMs,
but also combinations consisting
of more than one sound simultaneously (MIDI Multi Mode). To call
up the MULTI PROGRAMs, press
the MULTI button and select 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 PROGRAMs, the sounds
involved are allocated side-by-side
(split) or on top of one another
ACCESS VIRUS OS4
The Virus
19
(layered) on the keyboard. In other
MULTI PROGRAMs, 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 control
this MULTI PROGRAM via several
channels.
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.
Select the single program “A127 START -”. Press any key on the connected keyboard. 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 immediately after you
press a key and sustain indefinitely
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.
CHAPTER
20
Introduction
4
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
hearing, beginning with the volume characteristics. Locate the
section labeled
bottom right of the control feature
panel of the Virus. Here you can
see five pots labeled
DECAY, SUSTAIN, TIME
respectively.
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.
AMPLIFIER
ATTAC K
and
at the
,
RELEASE
Rotate the
repeatedly engage a key to hear
the note. The further you turn the
pot up, the longer it takes for the
sound to achieve maximum volume after the start of the note. So
you can say
initial volume swell of the sound.
Presumably the
set to a random position before
you made any adjustments. Nevertheless the volume automatically
increased to the maximum level
,
before you started rotating the
pot. The reason for this is that an
ATTAC K
sound program - START - and this
value remains valid until you
determine a new value by adjusting the position of the pot, even if
you turn it ever so slightly.
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 pot: at the left you
can see the value stored in the
sound program and at the right,
ATTAC K
ATTAC K
value of 0 is saved in the
pot while you
controls the
ATTAC K
pot was
ACCESS VIRUS OS4
The Amplifier Envelope
21
the numeric equivalent to the
value determined by the current
position of the pot.
Always keep in mind that for a
programmable synthesizer the
position of the control feature or
pot does not necessarily indicate
the actual value of the given function. The reason for this is that
when you first activate a sound
program, it will reflect the programmed value. You have to adjust
the control feature before the programmed value is superseded by
the value you determine manually.
Now fiddle with the
DECAY
pot
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
ATTAC K
phase, drops until it
reaches a minimum level. The
DECAY
pot 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 minimum levels at which the volume
remains constant. This level in turn
is controlled via the
Whenever the
SUSTAIN
SUSTAIN
pot.
level is set
to maximum, the volume cannot
drop during the
DECAY
phase; in
other words, in this situation the
DECAY
pot is ineffective.
The individual functions of a
synthesizer are designed to interact; many functions are dependent
on other functions. In a number of
cases this means that some functions are subordinate to others, i.e.
the effectiveness of a control feature is altered, modified or even
negated completely 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
CHAPTER
22
Introduction
4
lower the level, the shorter the
RELEASE
brief
phase. If you dialed in a
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 determined by the
TAI N-TIME
pot: If the pot is set to
SUS-
the center position (12 o’clock) indicated by the mathematical infinity
symbol, then the
SUSTAIN
level
remains constant through to the
end of the note.
If you turn it counter-clockwise to
the left (towards FALL), then the
level drops off at an increasing rate
towards the minimum level much
in the manner you just experienced with the
DECAY
pot; If you
turn the pot clockwise to the right
(towards RISE), the level rises at an
increasing rate to maximum and
remains there until you release the
key.
(turns it up or down). At the beginning of the note,
ATTAC K
controls
the rise or rate of increase to the
maximum level. Once the maximum level is achieved,
DECAY
determines the fall or rate of
decrease to the
SUSTAIN
value,
which is infinitely variable
between the minimum and maximum levels. The amplifier envelope may remain at this value until
the end of the note, fall towards
the minimum level as determined
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.
Consequently, the control pots
labeled
RELEASE
where as
ATTAC K, DECAY, TIME
and
control a speed or rate,
SUSTAIN
actually con-
trols a level.
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
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.
ACCESS VIRUS OS4
The First Filter
becomes muddier and clearer in
response to the direction in which
you turn the pot. (To ensure this
effect and the following aural
experiments are most pronounced,
adjust the amplifier envelope so
that the Virus generates a constant
level while you hold a key down).
This is how a low pass filter works:
it suppresses, or in technical jargon, attenuates the higher frequencies in a signal and allows the
lower frequencies through. Think
of the
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 socalled cutoff or filter frequency are
suppressed, those below it remain
unaffected.Now locate the FILT 1
MODE switch, which is also located
in the
you to select a filter operating
mode from the four available
options:
CUTOFF
FILTERS
pot as a bouncer
section. It enables
23
Locate the
confused with
section labeled
above the section labeled
FIER
. Rotate the pot to the left and
right and note how the sound
CUTOFF
CUTOFF
FILTERS
pot (not to be
2!) in the
, directly
AMPLI-
LLLLPPPP
the low pass filter we have
just discussed.
CHAPTER
24
Introduction
4
HHHHPPPP
the high pass filter which
works in the opposite manner of
the low pass filter: It suppresses
the lower frequencies in a signal
and lets the higher frequencies
pass.
BBBBPPPP
the band pass filter which
suppresses both ends of the tonal
spectrum and allows only a narrowly defined bandwidth of the
original sound to pass.
BBBBSSSS
reject filter or notch filter which
works in the opposite manner of
the bandpass filter. It allows all of
the frequencies of a signal except
for a narrow frequency band
around the cutoff to pass. The
term “notch” is fairly descriptive;
you might say this filter chops a
notch out of the sound spectrum.
The band stop filter, band
Now activate the different operating modes and rotate the
pot to get a feel for the way each
filtering option works.
Along with the
RESONANCE
tant control feature of a filter. The
filter resonance increases the volume of the frequencies located
near the cutoff frequencies and
suppresses the more remote frequencies. This sound shaping feature has a striking effect especially when used in conjunction with the low pass filter: it produces a nasal or honking type of
tone which increases as you turn
the resonance up. Experiment by
varying the
the different operating modes in
conjunction with different CUTOFF
settings. You will find the effect
that the RESONANCE pot achieves
is markedly different for the band
stop filter in comparison to the
effect it has on the other filter
types: as the resonance increases,
the bandwidth of the notch
decreases; in other words more
frequencies on both sides of the
filter frequency are allowed to
pass.
CUTOFF
pot is the most impor-
RESONANCE setting in
CUTOFF
pot, the
FILTER MODULATION
Of course we don’t want to require
you to execute every sound modification manually by twiddling pots.
All kinds of sound modifications in
the Virus can be executed automatically much in the way of your
previous experiments with the volume controls: 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 (turns it up or down) an
imaginary volume pot.
Similar procedures are applicable
to the filter frequencies. The FIL-
TERS section features its own envelope, the structure of which is
identical to the amplifier envelope,
located directly above the amplifier envelope on the control feature panel. Much like the amplifier
envelope, the filter envelope automatically “rotates” the CUTOFF
pot.
However there is one significant
difference between the two envelopes. With the amplifier envelope,
you are always dealing with an ini-
ACCESS VIRUS OS4 25
Filter Modulation
tial volume level of 0 because of
course you want absolute silence
prior to the beginning of a note.
After the RELEASE phase, it is again
highly desirable that your box is
silent. With the filter envelope, the
situation is somewhat different: It
always starts at the CUTOFF value
that you determined manually.
And it is definitely not always
desirable that the filter frequency
is brought to the maximum level.
Consequently, you need a tool that
limits the effective range of the filter. This is why we equipped the
Virus with a control labeled ENV
AMOUNT (short for Envelope
Amount). When the pot is turned
counter-clockwise to the far left,
the filter has no effect on the cutoff frequency; the further you turn
the pot to the right, the greater
the effect the filter envelope has
on the filter frequency. The maximum level of the envelope may lie
outside the audible range when
the filter has already been partially
opened via the CUTOFF pot or was
manipulated via other control
options. In extreme cases where
the filter is already completely
26 CHAPTER 4
Introduction
open, the filter frequency cannot
be increased regardless of how
high you set the ENV AMOUNT.
Go ahead and spend some experimenting with different ENV
AMOUNT, CUTOFF and RESONANCE settings for the diverse fil-
ter operating modes. Also try
varying the settings for the amplifier envelope. You will find that
with just these few parameters
you are able to come up with a vast
amount of sound settings. If you
are among the many musicians
who are associative listeners, you
might say many of the settings
produce sounds reminiscent of
stringed-instruments; some sound
picked, plucked or snapped, others
sound bowed.
For your next experiment set the
amplifier envelope so that you
hear a constant level when you
press and hold a note. Now deactivate the filter envelope by setting
the ENV AMOUNT to 0. Set Filter1Filter-1 to low pass mode and
decrease the filter frequency until
you just barely hear a muddy signal when you play notes in the
mid-range.
Now play a few higher and lower
notes. You will find that the lower
notes have a greater overtone content, whereas the higher notes
sound muddier and their volume
decreases until the notes are completely inaudible. You might
already suspect what this is all
about: As the notes are transposed
ever lower, more portions of the
signal fall below the cutoff frequency, whereas with the notes
that are transposed ever higher,
more portions of the signal rise
above the cutoff frequency and
subsequently are suppressed until
the root note and the last audible
portion of the signal is silenced.
To avoid this effect - or if desirable,
to amplify it - you have the option
of influencing the cutoff frequency
via the pitch of the note, i.e. the
note number. The degree of influence is determined by the KEY FOLLOW pot.
Please note that KEY FOLLOW is a
so-called bipolar parameter: Its
control range is not limited to the
positive end of the spectrum (0 to
a maximum of 127). Bipolar controls effect negative values as well,
in this case from the negative
maximum of -64 through 0 an on
to the positive maximum of +63.
Consequently, if this pot is set to
the center position (12 o’clock or 0)
the pitch of the notes corresponding to the keys on your keyboard
has no effect on the cutoff frequency. If on the other hand you
turn the KEY FOLLOW pot clockwise towards the positive control
range, you will find that the filter
opens up increasingly as the pitch
increases with higher notes. At
lower notes, the filter closes down
again. If you turn the pot counterclockwise towards the negative
control range, the KEY FOLLOW
effect is reversed. With the Virus,
you will encounter this feature intensity control via a bipolar
parameter - again in conjunction
with other modulation sources
and targets.
Now experiment as much as you
like with different KEY FOLLOW
settings and tune the settings via
the CUTOFF pot. And remember to
bring all of the other parameters
you have encountered thus far into
play.
ACCESS VIRUS OS4 27
The Saturation Stage
THE SATURATION
STAGE
In the signal chain of the Virus, Filter-1 is followed by a saturation
stage. It enables you to add overtones to the filtered signal via distortion. Locate and press the
button labeled EDIT in the FILTERS
section.
01111111111111111112
1 SATURATION
Curve Off≤
61111111111111111154
The display will read ”SATURATION
CURVE OFF”, which means exactly
what it says. With the VALUE buttons or the VALUE pot, you can
now select from a number of satu-
ration/distortion curves. Next to
the distortion curves, the SATURA-
TION stage offers further DSP
effects such as the shaper, rectifier
and filter. These are explained in
detail in the section on the SATU-
RATION stage.
At this point we would like to mention the OSC VOL pot in the MIXER
section. The portion of the control
range from the far left to the cen-
28 CHAPTER 4
Introduction
ter position (12 o’clock) determines
the volume of the filter section’s
input signal. The portion of the
control range located to the right
of the center position (12 o’clock)
does not achieve any increase in
volume; it simply intensifies the
degree of saturation or distortion.
This effect is only achieved when
you have activated a saturation
curve. The intensity of the remaining available DSP effects is also
controlled via the OSC VOL knob.
Feel free to experiment with the
diverse saturation curves and be
sure to vary the OSC VOL settings.
Note how the different CUTOFF
and RESONANCE settings influence
the saturation curve.
THE SECOND FILTER
You probably noticed that by a
adding a bit of saturation to the
signal you can come up with a
pretty heavy, aggressive sound especially with a low filter frequency level and high resonance.
You’re probably thinking these
types of sounds could do with
some more filtering. We had the
same idea, which is one of the reasons why we equipped the Virus
with another filter per voice.
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