Although the Access Virus features one of the most knobby control surfaces amongst virtual analogue synths, there's a lot of programming flexibility available which isn't immediately obvious. We show you how to uncover the hidden possibilities...
The Access Virus is one of the more successful virtual analogue synths, and its ballsy, punchy sound has been enthusiastically adopted by musicians working in a wide variety of musical styles. However, for programmers and sound designers this isn't the easiest synth in the world to get to grips with. The fact that there are knobs on the panel is deceptive, because they control fewer than half the available parameters. Getting to the rest needs either a computer-based editor or a good head for menu navigation and a sturdy index finger. In this article I'll be offering a number of hints and tips for programming the Access Virus B specifically, but because the Virus has changed relatively little, most of this advice also applies to other models, from the earliest Virus A onwards.
The basic editing principle is simple. Each section — oscillators, LFOs, filters and main control — has its own separate Edit button. These buttons don't interact (in other words, Access didn't choose to make them link into a single very long menu list), but if you remember that the only way to get to some of the parameters is through the different Edit buttons, you won't go wrong. For overall instrument control, use the Ctrl button, which sets various global parameters. All the other Edit buttons are patch specific.
The other confusing feature is display snap. Whenever you alter one of the knob settings, the display changes to show that parameter. Then it snaps back to whatever was being shown before. This can be confusing initially, but after a while it starts to make enough sense to be usefully informative.
With those basics in mind, let's take a closer look at the oscillators. These have been designed to produce both digital and analogue effects. But they can leave programmers quivering with confusion, because the shaping options are controlled by just two knobs, the functions of which are completely misrepresented in the manual. Figure 1 is a block diagram showing how the controls really work. What you get are three sources, crossfaded by the Shape knob: at 12 o'clock there's a static sawtooth; at the maximum anticlockwise setting there's a wavetable oscillator; and at the other extreme there's a pulse oscillator. The Wave Sel/PW knob does double duty, controlling the waveshape for both the wavetable and pulse sections. The sawtooth, meanwhile, is completely static, and no amount of Wave Sel waggling or modulation will ever change it.
One obvious limitation of the way the controls work is that you can't hear pulse and wavetable outputs together — perhaps not a major drawback, but it's as well to be aware of it. Another 'gotcha' is that the pulse-width range available via the Wave Sel knob is limited to 50-100 percent, rather than the 0-100 percent range you might want. The only way to get the full range is to add modulation from the envelopes or LFOs using the modulation matrix, of which more in a moment.
So, as a rule of thumb, the best way to get interesting effects from the oscillators is to leave the Shape parameter alone, usually at one extreme or the other. If modulation is going to be used, apply it to Wave Sel only. At the digital extreme, it's worth taking some time to set up a manual sweep so that you can note down which wave numbers sound the most interesting. For example, waves one and two are sine and triangle respectively; wave 64 is good for vibe and marimba effects; wave 14 is a good organ tone; and wave 57 has a fifth mixed in, which makes it good for solos. When used with some low-pass filtering, many of the waves are good raw material for DX-like percussive sounds, and electric pianos are also easy to create. (Note that there are no good vocal waveforms, but as we'll see later there are ways around this shortcoming.) Treating the Virus as a simple single-oscillator synth offers a wide enough sonic universe that it really is worth taking the time to get familiar with the raw materials available here.
- Virus, SOS May 1998.
- Virus B & Virus KB (Virus OS v3), SOS February 2000.
- Virus Indigo (Virus OS v4), SOS June 2001.
- Virus Rack, SOS October 2001.
- Virus C (Virus OS v5), SOS August 2002.
- Virus Indigo 2, SOS October 2002.
- Virus Indigo TDM, SOS September 2003.
- Virus Indigo Redback (Virus OS v6), SOS November 2003.
The wavetables step very obviously while scanning, and lack the smooth changes between closely related tables available in some PPG-type instruments. But more coarse timbral stepping effects can still sound interesting. For example, routing the velocity values of MIDI Note On messages to Wave Sel is a quick and effective way to add timbral control to sequences and bass lines. (It's not so useful for manual control, unless you have the exquisitely toned and sensitive fingers of a top classical pianist, with a controller keyboard to match!) For a more extreme effect, you can use the velocity values of MIDI Note Off messages to add extra stepped changes within each note, so that the timbre changes when you release a key.
A worthy challenge is to create evolving Wavestation-like pads. Because the wave selection is stepped rather than continuous, you can't do this by modulating Wave Sel. But if you set the three oscillators to different fixed digital wave shapes you can then use the LFOs or the envelopes to crossfade between them — not as complex an effect, but one that can still sound good with careful fine-tuning.
At the virtual analogue end of the Shape control's travel you can create some very punchy effects in the time-honoured analogue way by patching an LFO or envelope to control pulse width. This routing sounds particularly good on the Virus, and no owner should be without at least a couple of patches that do this. You can also mute an oscillator to match a beat by sending its pulse width to the 100-percent extreme with an LFO. Use a square LFO waveform to switch it on and off, or other waveforms to fade it. This sounds mind-bendingly extreme if you patch each LFO to a separate oscillator, and detune oscillator two up by a musical interval such as a fifth (+7 semitones). A less extreme effect is to detune the oscillators by a small amount and use this technique to add movement as the oscillators fade in and out, changing pulse width as they do so.
Modulating Shape offers fewer possibilities than modulating Wave Sel — which means you're usually best off ignoring the fact that Shape is one of the default destinations available on LFO2. But it can be interesting to crossfade between digital and analogue wave shapes using the envelopes, perhaps creating a sharp percussive digital 'donk' at the start of a note, and ending with an analogue tail. This can work well if you leave Wave Sel fixed. Trying to sync Shape modulation with Wave Sel changes can easily get unwieldy, and it takes a rare level of persistence and adventurousness to create listenable patches that rely on both effects. But as we'll see below, the LFOs have a few tricks that make Shape modulation more useful than it would be otherwise.
Although Access have done their best to confuse everyone about the different Virus models, the most basic developments and modifications are very straightforward, and the architecture has remained similar throughout. The main changes are extra polyphony in later variants (from 12 voices in the original Virus A to 24 in the Virus B and Classic, to 32 in the Virus C series and Indigo 2) and some extra modulation slots. The Indigo, of course, also has funky blue LEDs instead of yellow ones, and the Virus C is black/grey as opposed to the original red. The new Classic, which is more or less a Virus B reincarnated at a lower price, is even redder.
Perhaps the biggest update to the Virus C is the addition of a Moog-style filter mode. It's traditional to hype all things Moog-like, but in this instance the new filter more than lives up to expectations. There have also been some minor panel changes on the Virus C, with some new knobs and switches for LFO and oscillator control, but the outline remains familiar — anyone who has used one Virus should have no trouble adapting to a different one. The keyboard variants simply add a keyboard, whereas the XL variant, which put a Virus C inside a 1U rack, was not a success and has now been discontinued.
The Virus has also always been available as a plug-in. Sadly there's no stand-alone VST or DirectX version, but in the meantime there are two variants available for accelerated hardware, using the TC Powercore and TDM Pro Tools systems. Individual polyphony is limited to 20 voices, but with an appropriate license it's possible to run multiple copies for a maximum polyphony of 160 voices in a Pro Tools system. Architecturally these variants are very similar to the hardware models. The virtual control panels are rather plainer, but this doesn't affect the sound.
Oscillator two is just like oscillator one, but with extra Semitone and Detune settings. Also available are FM and Sync options. Sync works as you'd expect. One handy tip is that oscillator one has its own Semitone setting buried inside the oscillator Edit menus. Using this, you can tune it down a couple of octaves. Now when you select Sync, oscillator two can provide some very rich and broad static timbres depending on the relative pitch offset. Mix in the output of the sub-oscillator, and you have a very impressive sub-bass. You can create all the usual ripping sync effects by modulating the frequency of oscillator two with either an LFO or one of the envelopes.
The FM feature is more complex than Sync, with more sources to choose from. As with Sync, the destination is always oscillator two, but the source can be oscillator one's wave, noise, or an external input. Oscillator one's Tri, Pos Tri, and Shape (which uses the digital output controlled by Wave Sel) options speak for themselves, and the best way to hear the differences between them is to try them. Each has a different sweet spot, where the FM Amount setting aligns all the overtones in a way that eliminates beating and produces rich and reedy timbres instead of clangy ones. Sometimes the FM Amount resolution is too coarse to find this sweet spot exactly, and when that happens you can use oscillator two's Detune control to compensate. If you want clangy effects or ones with lots of beating, you can create them using the Semitone, Detune, or FM Amount knobs in any combination. Note that you can also control FM Amount using the envelopes. This can sound a tad too abstract, in a Dr Who kind of a way, for pads, but it can add a hint of extra punch and slap to bass sounds and leads.
An unusually interesting source for FM is the noise setting. This adds a kind of filtered noise effect around the pitch of oscillator two, and is good for grungy, dirty, quasi-distorted noises. Small FM Amount settings add an interesting hint of this. At large settings the sound falls apart into something that sounds like distortion of extreme nastiness. The sound responds to the Noise Color setting (also in the oscillator Edit menu), and negative settings have much more low-end rumble. If you detune oscillators one and two as low as they go, you get stepped transients which can trigger classic random analogue blips if fed to the filters with the Resonance knob turned up. Turning on Sync and dialling in extreme modulation of oscillator one with plenty of noise on oscillator two creates huge sheet-like ripping sounds. In between there's a range of timbral possibilities which is ideal for grungified distorted solo sounds. The FM section also includes two external stereo inputs. You can mix either of the two stereo inputs to mono sums, or select any of the four inputs separately, and then feed them into this section. Vocals work surprisingly well here, assuming you like industrial music — delicate processing for ballads is not this feature's strong point!
Hiding out of sight in the oscillator section are oscillator three and the sub-oscillator. The latter is a very simple low-end fattener, one octave down from oscillator one, with either square or triangle waveforms. A panel knob in the oscillator mixer section lets you set the level. Oscillator three will either follow oscillator two's settings if Slave is selected, or can be used as a spare extra waveform. FM and Sync don't affect oscillator three, so you can use oscillator two for richness and distortion while filling out the body of the sound with oscillators one and three. Note that using oscillator three cuts down polyphony by around a third — there aren't many situations where it makes a life-and-death difference to the size of the sound, so for patches you plan to use multitimbrally its use is perhaps best considered an optional extra.
The basic details of the Virus's various filter modes and patches are described comprehensively in the manual, and there's no need to repeat them here. Less well known are some of the effects that are unique to a dual-filter design and aren't based on the classic filter opening/closing effect.
Eliminating Muddiness: Too many patches based on low-pass filters can make the low end of your mix sound muddy. A static high-pass filter in series with a low-pass filter can remove some of the obesity, adding clarity to pads, leads, and even bass lines. Just set filter two to work as a high-pass filter, and put it in series after filter one. Then move the cutoff of filter two upwards until you get rid of the low-end bloat.
Aside from some dance styles and music with ultrasonic effects, most music benefits from having the low end tidied up. This can help preserve detail and avoid synth mush, especially when blending a lot of analogue-like patches. It can even allow you to maximise the apparent level, because faithfully reproducing deep sub-bass frequencies takes a lot of dynamic range for little subjective impact. It can even be worth tidying up the low end when you don't have the oscillators tuned low. This is because the envelopes on the Virus are fast enough to produce near-DC clicks, pops, and thuds. Sometimes you want to leave these in because they add extra punch to sounds, but when you don't a high-pass filter is a good way to get rid of them.
Pseudo-phasing: Most synth users understand how a filter's frequency curve changes, but it's not so widely known that a filter produces frequency-dependent phase changes as well. Overlaying two filter curves produces more than the sum of the individual responses, and sweeping either or both can create Jarre-like phasing effects that vary depending on which filter modes you use. This isn't true phasing, which relies on multiple notches in the frequency response. But it can produce some very fine swishes and washes, and can work particularly well combined with vamped chords from the arpeggiator. Use the Par 4 mode for this, with one filter set to low pass or band pass and the other as either high pass, band pass, or band stop. You can manually experiment with the effect by using the Cutoff 2 knob which, as the manual explains, controls the offset between the two filter frequencies and is not — as you might think — an independent cutoff setting.
Vocal Formant Effects: High-quality vocal formant synthesis needs at least three filters, and for the best possible results five. But you can still create some interestingly vocal-like effects using just two filters if you set things up very carefully. The first step is to create some speech-like raw materials. The vocal chords make a buzzy clicking sound very like a thin pulse, so begin with a single oscillator, setting Shape to its maximum value and Wave Sel/PW to around 115. Then set both filters to band-pass, mode to Par, resonance to around 90, and filter keytracking to zero percent. You'll get a range of vowel sounds by setting both Cutoff controls between 50 and 70 — experiment for best results. For an even more expressive effect, patch the mod wheel to the Cutoff 2 control. You can then play the vowels as you play the keyboard. The effect only sounds believable over a low 2-3 octave range, and works best as a solo voice. If you patch velocity to Cutoff 2, you can control the vowel sounds from a keyboard (interesting, but tricky to play...), a sequencer, or the built-in arpeggiator.
Saturation: Although this is controlled with the oscillator Volume knob, the saturation is part of the filter section and you can set its characteristics from the filter section's Edit button. The Virus offers a range of saturation types, from basic rounding to digital decimation. These are best experienced rather than described. Many add a hint of digital fizz that isn't always welcome — it's a quirk of the Virus that for analogue simulations you'll often get the best and fattest sound by leaving saturation turned off.
The home site for the Virus and its many variants. Includes OS updates for all models, comparison charts, sample MP3s, patch collections, and links to other resources. Plus, you can download the free Sound Diver-based editor from here as well. It's perhaps because the support network available here is so comprehensive that there's so little other on-line information about such a popular synth.
- Ampfea's Access Mailing List
The Access mailing list on Ampfea. Because it's maintained by fans, there's more general than technical chat about the Virus and how it's being used.
- Rob Papen's Home Page
Home of Rob Papen, who contributed many of the most popular patches to the factory set, with a link to patches that Rob sells online.
Like the other features of the Virus, the LFOs have plenty of hidden subtleties that can baffle the novice and delight the adventurous sound designer. The basics seem straightforward enough — two LFOs with the usual selection of wave shapes and destinations — but the Wave LFO setting is one of the secret weapons in the Virus arsenal. Pressing the Shape button on the panel shows the wave selector. This offers standard stepped sample and hold (S&H), smoothly varying sample and glide (S&G), and access to all of the digital waveforms that are available in the oscillator section. This might not sound like a big deal, but the Virus really comes alive when these digital waveforms are used as modulation sources. They're particularly useful for controlling the amplitudes of the oscillators in various combinations, and for complex filter sweeps. The standard sine, triangle, and ramp waveforms sound predictable and uninteresting in comparison. (As a side note, if you see a Virus with LFO LEDs flickering apparently randomly, it's likely that the LFOs have just been set to produce the digital oscillator waveforms.)
When combined with the arpeggiator, it's easy to use these waves to create complex but solidly rhythmic textures that evolve as notes are held down, these patterns spanning anything from a fraction of a beat to entire bars. As with the oscillator section, it's well worth taking the time to audition these waves to see what kinds of effects they can create when used as modulation sources. For example, wave 47 is a double ramp, and is particularly good for rhythmic modulation. Some of the other waves change very quickly, which means they're best used at very slow LFO rates. Unfortunately there are no wave graphs in the manual, and so far as I could find they're not listed anywhere on-line either.
These more complex waveforms work particularly well when you combine them with MIDI sync. By default LFO timings are absolute, but if you change the Clock setting, within the LFO Edit menu, you'll see a range of MIDI clock dividers, from tiny fractions of a beat to 16 bars (shown as '16/1'). The wide range is there to accommodate some of the more frenetic modulation shapes. With a little thought it's easy to create very complex but stable rhythmic effects by locking both LFOs to MIDI clock, setting each one to a different subdivider and waveshape, and then routing them to Wave Sel, filter cutoff frequencies, the levels of each oscillator, the pitch of oscillator two when the Sync button is turned on, and so on. But how to make these connections? The selection of default assignments available from the panel is more than a touch random. Oscillator pitch is obvious enough, but LFO control of filter resonance isn't quite so useful and, as we've seen, control of oscillator Shape is less useful still. Fortunately, the Assign option provides a much wider range of destinations for both LFOs.
Clicking the button repeatedly steps down the list of destinations on the panel. When the Assign LED turns on, 'Dest' appears in the edit window. Now you get a huge range of destinations to choose from, including almost all the programming parameters the Virus has to offer. Aside from conventional patching possibilities (pitch, filter cutoff, and so on) there are also more adventurous destinations, such as the envelope timing parameters and arpeggiator controls. You can also modulate effects settings, such as delay time and reverb mix. You can even make the LFOs modulate each other, for chaotic and unpredictable effects.
When you combine complex waveforms with MIDI sync and this very rich selection of modulation routings, you can add another level of movement to rhythmic patches, or create very fluid and interesting slowly evolving pads and abstract tones. The patching possibilities rival those of a medium-sized modular, but with the advantages of MIDI sync, polyphony, and patch memories. It's perhaps best to explore these combinations without too much direction from a feature like this one. The basic principle of using unusual LFO waveforms with MIDI sync and perhaps the arpeggiator gives you plenty of scope for colourful sound creation. As with a real analogue synth, exploring the possibilities makes finding some trademark programming effects and a signature sound more likely.
- In the Ctrl menus you'll find Random Para Depth and Amount settings. Depth sets the number of parameters that are randomised, and Amount sets the scale of the changes. A large Depth will change effects parameters as well as patch basics. This section is incredibly useful for creating sounds and patches you wouldn't invent on your own.
- You can control the arpeggiator pattern number with an LFO or other modulation source. This might not seem hugely useful, but it's a good way to create a rhythmic riff that's always changing. With careful fine-tuning this can be a surprisingly sophisticated effect.
- The latest OS updates include some fancy delay modes in the delay/reverb section. The delay time can be locked to MIDI Clock, and these modes produce different multiples of a sub-beat for left and right channels. For instance, '1+4' means 1/16 of a beat at the left and 4/16 at the right). When combined with the arpeggiator, these sound truly wonderful.
- Older versions of the Virus took a rather random approach to sync'ing using MIDI Clock. The arpeggiator would start when you hit a key, which could sometimes be some way off the beat. On the Virus B, OS v4.07 (and higher variants on other models) solves this problem by estimating beats from MIDI Clock start. This makes live arpeggiator performance considerably easier, but also loses some of the feel you could introduce by deliberately playing ahead or behind the beat. If you prefer the original random approach, you can find older versions of the OS archived on the Access web site.
- Although the Virus lacks an 'analogue detune' parameter, you can simulate it by setting the first LFO to Wave and using the modulation matrix to patch a small amount to each of the oscillators. This creates the classic analogue 'not quite in tune' effect. Make sure the LFOs are working polyphonically, otherwise you'll get a patch where the pitch wobbles are alarmingly in unison.
- A feature in the newer models and OS updates lets you write your favourite patches to the ROM banks. In the System menu, find Store To Flash, select which banks you want to copy, and then wait while the internal flash programmer rewrites the flash ROM. You can only save entire banks, so its best to get your patches organised first using the Sound Diver utility before attempting a burn.
And what about that arpeggiator? By default it has the usual selection of modes: up, down, random, and so on. These aren't very exciting, but using the Pattern parameter brings in a range of rhythmic repeats that spice up the sound and make it much more interesting. There are 64 of these (if you have an older OS you'll find fewer available — you can get the rest by upgrading) and they use the same clock divider system as the LFOs, so it's easy to create MIDI sync. At very fast subdivisions, such as 1/64, you can create whirring distorted effects.
The arpeggiator also hides a secret, which is that notes in each pattern include velocity information. So patching velocity to filter cutoff, Wave Sel, or some other timbral parameter can produce some wonderfully dynamic rhythmic effects. As a good rule of thumb, most patches with a fast attack sound good when arpeggiated this way, and it's worth spending a productive hour or two trying out arpeggiation on all the presets that don't have it already. The top 30 patterns or so include twiddles, legato glides, and burrs designed to add interest to dance music. Many of these sound best in one of the Mono modes, and turning manually-controlled portamento on can create some very TB303-like acid effects.
Using the arpeggiator in Multi mode can easily create monstrous arpeggios of ultimate doom! The trick here is to try to use patches and pitches that are distinct enough to be heard clearly. You can also add basic rhythm by filling out the sound with arpeggiated bass drum, snare, and hi-hat patches — the latter especially can benefit from some of the more intricate patterns that are available.
The effects section of the Virus is an understated beast. Each voice in the Virus C has its own completely independent effects chain, with phaser, chorus, delay/reverb, and three-band EQ. Although you can use these effects just for adding gloss to your synth sounds, it's more interesting to include them within patches in a more organic way. The key here is the modulation section buried deep inside the main Edit menu. This works like the LFO assignment section, but is independent of it and offers a much wider range of sources, including various MIDI controllers, velocity, and also the envelope outputs. The destinations include most of the parameters inside the Virus — including many effects control parameters.
This means, for example, that you can use an envelope or one of the continuous controller channels to control delay time or phaser frequency. A good start is to experiment with adjusting the effects using the synth section's modulation sources. Doing this will give you a whole new palette of sounds and effects you probably never expected to hear from a synth.
And finally, there's external processing to think about. Access have made it easy to assign external inputs to oscillator control for FM, to the ring modulator, and of course to the filters. The big attraction in the last case is that this will also route audio through the effects section, so you can use filtering and level control at the same time as adding delay effects and chorus — ideal for chopped up dance pads, for example.
But perhaps the most impressive effect which uses the external inputs is the vocoder. The manual does a good job of explaining how this works, and if reading about it doesn't make it clear, practice soon will. What's not so obvious is that the vocoder parameters can be programmed and sequenced via MIDI using the standard Virus panel assignments. This gives you total control over spread, bank offset, resonance, and all the other ingredients of the vocoder sound, and setting up rhythmic MIDI control can create some extremely dynamic and unusual effects. If you have a MIDI processor like Cycling 74 Max/MSP or Emagic Logic, you can even route the output from the arpeggiator to these parameters in real time.
It's likely that many Virus owners aren't using their synths to maximum effect. However, unlike other synths where intensive patch programming produces sounds that are more gimmicky than interesting, the Virus is an extremely musical product and will enthusiastically repay an adventurous approach.
If you'd like to hear how the programming techniques in this article work, then audition the following six audio files (in the righthand sidebar of this article):
- wavesel.mp3. This shows how you can create timbral changes by routing the velocity values of incoming MIDI note messages to the Wave Sel control.
- lfopad.mp3. Here LFOs modulate pulse width and also fade the different oscillators in and out, thus creating movement in the pad sound.
- fmblips.mp3. The stepped transients that you get in FM mode by detuning the oscillators as low as possible can tease a variety of textures out of the filter section when its resonance settings are up high.
- vocalfx.mp3. If you set the filters up carefully, it's possible to get vocal formant effects which can be controlled by MIDI note velocities.
- lfoarp.mp3. Combining the effects of some of the Virus's more complex LFO waveforms with those of the arpeggiator, you can create rhythmic chordal patterns which evolve over long periods.
- vocoder.mp3. Here a synth line has been fed through the vocoder while the vocoder's parameters are modulated over MIDI.