A year or two before the Minimoog and ARP 2600 were
introduced and started to standardize the voice design of a portable
performance synthesizer, EMS was already producing the VCS3. Features
that we take for granted today, such as separate envelope generators for
the filter and amplitude, were not to be found, but a very
forward-looking patching matrix was. Though overshadowed by later
instruments, the VCS3 was used by a number of well-known artists in the
early 1970s, including Brian Eno, Pink Floyd, and the Who. XILS 4 is a
high-octane software clone of the VCS3. Scroll past the video for our full review.
XILS 4 retains the unique sonic character of the original,
and also some of the quirks, while adding a host of new features,
including polyphony, adjustable levels on all of the matrix patch
connections, many more patch connections than on the original, effects,
and dual operation with two independent VCS3 synthesizers side by side.
It runs as a VST, AU, RTAS, or AAX plug-in. The authorization requires
an eLicenser or iLok hardware dongle (not included in the purchase
price), but the downloadable demo is dongle-free.
In XILS 4, all signals are handled at audio rate. This
gives you more sonic power. It also means XILS will use more of your
computer’s CPU cycles. Assuming you have a fast computer, you should be
Depending on how you do the patching, XILS 4 can be either
a six-oscillator synth or two three-oscillator synths. One of them can
respond to the keyboard while the other responds only to the built-in
step sequencer, but they have no key range or MIDI channel settings, so
you can’t set up two independent hand-played parts using one instance of
It’s entirely up to you how to configure the signal
flow—and that’s both a strength and a stumbling block. There is only one
internal “hard” connection: between the envelope of the left or right
section and that section’s amplitude VCA. Everything else, including
keyboard gate and trigger signals, has to be patched by hand.
Fortunately, the instrument is well supplied with
tasty-sounding factory patches, so you won’t need to master the details
in order to start making music. But when you start customizing the
patches, you can expect to do a bit of head-scratching.
The left and right sections are identical except for one
important feature: The left side has a pair of external audio inputs,
while the external inputs on the right side receive output signals from
the left side.
Each side has three oscillators with wave-shaping, a noise
source, a ring modulator, a resonant lowpass filter with three
selectable roll-off slopes, an envelope generator, a modeled spring
reverb, and non-resonant lowpass/highpass filters for the left and right
outputs. The cutoffs of the output filters are one of a very few things
that can’t be modulated in real time from within the synth, but not to
worry: You can control them via host automation or MIDI CC messages.
In addition to the left and right synth panels, there’s a
third global panel containing a variety of modules — an LFO, two extra
envelope generators, a voltage processor, a sample-and-hold, three
effects (chorus, phaser, and delay), a complex step sequencer, and four
audio input sensors (a pitch tracker, an envelope follower, a transient
detector, and a gate).
The input sensors allow you to use XILS 4 as a very
capable insert effect. It can easily filter or ring-modulate an audio
input. You can even patch a signal through its spring reverb emulation
and then ring-mod and filter the reverb output.
The secret sauce in XILS 4 is the Analog knob. This adds
instability to the oscillators’ frequency, and possibly to the filter
cutoff as well. In most of the factory sounds, this knob is set to 50
percent, which is just about right for a slightly unstable vintage tone.
The instability is more jittery than the typical oscillator drift heard
on other software the tries to emulate analog hardware. With simple
patches, the jitter can be a bit obnoxious, but with a more
sophisticated patch, you won’t notice it consciously; it will just make
the sound more lively.
MIDI control change messages can be mapped to the knobs of
your choice using a standard Learn operation. Unfortunately, there
seems to be no way to unlearn an assignment, other than by using Learn
to make a different assignment. Typing “none” or an unused CC number in
the data field in the dialog box doesn’t work. This area of the software
needs more work.
Not only does the XILS have a lot more matrix patching
possibilities than a hardware VCS 3, it’s possible to patch signals from
the left side into the right side. As a result, setting up a patch with
separate filter and amplitude ADSR envelopes is easy.
Unlike the VCS3, which accomplished patching with physical
pins, XILS gives you a bidirectional mini-knob (it’s shaped like a
little red triangle) for each connection. Because the patch panels are
small, a handy magnifying-glass button has been provided for zooming in.
As you adjust the level of a connection, a pop-up shows its current
value, and temporary white lines direct your attention to the input and
output whose connection you’re editing. Right-clicking cancels the
connection. This is a neat and powerful system, and also overcomes the
very significant electronic limitations of the VCS3’s patching
mechanism. (The resistors used in the pins didn’t all have the same
values, and the pins tended to get lost.)
There are two patch panels for each side, the Main and
Extended panels. The Main panel is similar to the patch matrix on the
VCS3. It has signal inputs from all three oscillators, the noise source,
the ring modulator, the joystick’s X- and Y-axes, and so forth—yes,
there’s a mouse-operated joystick. The outputs are intended to receive
either audio signals (the audio outs, the VCA, the reverb and filter,
and so on) or control signals (for oscillator frequency, filter cutoff,
output level, and so on). If this sounds a bit bewildering, it’s because
the possibilities are vast.
The Extended panel, intended mainly for control routings
rather than for audio, has inputs from oscillator 3 (which is intended
as an LFO), the audio input section’s pitch tracker and envelope
follower, various MIDI inputs, and so on. The outputs are for oscillator
shaping and frequency, filter cutoff, envelope generator decay, and so
on. There are also two selectable inputs and four selectable outputs.
The selections here include signal sources and destinations in both the
left and right synth panels, so it’s a simple matter to do tricks like
frequency-modulating a right-side oscillator from one on the left side.
Because the oscillators and filter can be patched directly
to the outputs, bypassing the envelope-controlled VCA, creating drone
patches that start as soon as they’re loaded is as easy as anything
Each side has its own envelope generator. In addition,
there are two supplemental EGs in the third panel. Each of the four EGs
can operate in either of two modes—the “trapezoid” mode found on the VCS
3, or as a more modern ADSR. Trapezoid mode has attack and decay time
knobs, plus a hold time knob (labeled “on”) and an off time knob. If the
off time is less than infinite, the envelope will loop. In Trapezoid
mode the envelope doesn’t respond to sustained keyboard notes; it just
goes until it has passed through the attack, hold, and decay times, and
When the off time is reduced so that the envelope loops,
any of the knobs will also change the total length of the loop, so
there’s no practical way to sync a looping envelope to anything. With
short loops, helicopter and burglar alarm noises are quite feasible. In
normal operation, the looping does stop when you lift your finger from
the key, but that behavior can be overridden. If you unhook the
connection between Keyboard Gate and Trapezoid (either left or right)
XILS becomes a polyphonic rhythmic drone machine.
Effects and Output
XILS 4 has no master output volume. Instead, the output
section in each synth panel has separate level and pan knobs for signal
paths 1 and 2. These signal paths in the separate panels also have
fixed-frequency non-resonant filters, which can be either highpass or
lowpass. By using one of each type and panning the two signals to the
center, you can create a fixed-frequency notch filter.
The stereo delay effect takes its inputs from these output
buses after the pan controls, so you can set up a highpass delay on one
side and a lowpass delay on the other side, with separate time and
feedback settings. The delay effect is syncable.
The phaser is has a nice tone, and can self-resonate. The
chorus is simple, and has a distinctly vintage tone. One of its three
modes filters the delayed signal. Another uses only a single delay line,
so you can get Farfisa-like vibrato by setting the wet/dry knob to full
Each side has its own “spring reverb.” These modules sound
remarkably cheesy—which is what they seem to be going for. Other than
the delay time and reverb wet/dry, the effects modules can’t be
controlled via the pin matrix.
The sequencer has some powerful features, but it’s not the
easiest module to figure out. It can have up to 128 steps. There are
three separate sequences, each with two layers, so the sequencer can
output up to six independent control signals, plus trigger signals for
the envelopes. All three sequences will be the same length, but each can
have its own pattern of rests. There’s no way to modulate the clock
rate using an internal signal path, but it can be automated in the host
The upper layer in each sequence has a slew rate control
for pitch glides, but the lower layer doesn’t, the assumption being that
you’ll probably use the lower layer for velocity data. You can easily
use it for pitch if you want to, though. The sequencer can be gated on
and off from the keyboard, and it’s up to you whether you want the
oscillators’ pitch to track the keyboard while also responding to the
The graphic editing of the sequence data is not fancy, but
it does the job, at least with shorter sequences; there seems to be no
way to zoom in on the data in long sequences, so a rather fussy step
editing process will be required. Other features include the ability to
run in one-shot mode and MIDI-controllable stop and reset buttons. The
patchable outputs for the six layers are oscillator waveshape,
oscillator frequency, envelope decay time, reverb level, filter cutoff,
and output level. Individual control from the sequencer over parameters
like attack time, noise generator amplitude, and filter resonance is not
You can save and load sequencer presets, but in the 1.0
release of XILS 4, trying to do this fails until after you’ve used a
menu command to create a random sequence for the first time. I’ve
reported the bug.
Some computer company or other once used the slogan,
“Think different.” XILS 4 is different. It’s a deep and flexible
instrument, and it’s capable of doing sounds, especially vintage
electronic tones, that no other synth can duplicate. As I checked out
the factory patches, I found myself reminiscing about the old Doctor Who series, whose soundtrack circa 1980 often used sounds like these.
XILS 4 is more difficult to program than most software
synths, both because of the need to patch even simple signal routings
manually and because a few of the modules behave in odd ways. If you
need meat-and-potatoes string pads and electric pianos, XILS 4 may not
be your best choice. But if you expect the unexpected, it may well blow
your socks off.
Powerful features for synthesis. Great for vintage tones. Works well as an effects processor.
Difficult to learn. No multimode filter. Effects are basic.
Vintage synth power on steroids.
$199 list | $149 street