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XILS Lab Synthix

Software Synthesizer
By Gordon Reid

XILS Lab continue to trawl the depths of obscure synth history, this time with an emulation of that rarest of beasts, the Elka Synthex.

XILS Lab Synthix

The first two soft synths from XILS Lab were certainly notable, both for their sounds and their facilities, and I think that it's fair to say that the XILS 3 and PolyKB II rank amongst the best soft synths yet produced. Now the company have turned their attention to another super-rare synthesizer, the Elka Synthex. A commercial flop, the Synthex now boasts a reputation that would have seemed impossible when it was discontinued in 1985, but is that enough to justify a dedicated soft synth?


A Synthix oscillator.A Synthix oscillator.

Like its inspiration, the Synthix is a dual-oscillator polysynth with a multi-mode filter that allows it to generate sounds that are not available from many classic analogue polysynths and their 'soft' descendents. It also recreates other unusual facilities that set the Synthex apart, such as its on-board chorus and four-track sequencer. However, compared with the original Synthex, Synthix boasts more waveforms, more contour generators (four instead of two), more modulation sources (five instead of two), routes and destinations, more effects (four instead of one) … well, more of everything.

Let's start by comparing the Synthix oscillators with those of the Synthex. Although these look somewhat different from the original's, closer inspection shows that they offer much the same facilities. The octave range is duplicated, coarse/fine tuning (called 'Transpose') is as before, as are the four waveforms. Pulse Width Modulation (which is actually Pulse Width cross-modulation from oscillator 2) is also retained, as is Ring Modulation, with knobs for initial PW and level. With oscillator sync and white/pink noise provided elsewhere on the control panels, there is one visible addition on the soft synth; you can defeat keyboard tracking if desired. There are also numerous hidden additions. For example, the triangle wave has a sine-wave option, and the sawtooth wave is capable of 'super-saw' effects, while the Width knob also controls the shape of the triangle wave and the depth of the super-saw wave.

Multi-mode filter.Multi-mode filter.Likewise, Synthix's filter is a combination of the old and the new. The Frequency and Resonance controls are present and correct, as are the contour amount and keyboard tracking knobs. Most important, all four of the Synthex's filter modes are retained, which means that you have access to all of the less usual band-pass and high-pass filtered sounds that helped to differentiate the Synthex from the Prophets, Oberheims and Moogs of the era. There's even an additional 12dB/oct LPF mode, and all five modes will self-oscillate, which is welcome. I wondered where the inverted envelope button had gone, but the AMNT and KEYB knobs are bipolar, so you can apply inverted envelopes and negative keyboard tracking by turning them anti-clockwise from the 12 o'clock position. A major addition is that drive can be applied at the filter input or after the filter to overdrive the amplifier. In both cases, this thickens the sound and is, again, welcome.

LFO, Chaox and Modulation Matrix modules.LFO, Chaox and Modulation Matrix modules.Despite the similarities so far, things start to look different when you inspect the contour generators and modulation capabilities of the original and the soft synth. Most obviously, there are just two ADSR contour generators on the Synthex, while there are four D(elay)ADSRs on Synthix. Likewise, no fewer than four programmable modulation generators have replaced the Synthex's single programmable LFO. These are LFO1, LFO2, Chaox (a quasi-random X/Y modulator that you can route to one of 38 destinations on each axis) and Rhythm, which generates a selection of ramps and pulses on what the manual calls the 6th, 8th or 16th steps. I asked XILS Lab what this meant, and they explained that they've divided the LFO cycle into (up to) 16 slices, and that the ramps and pulses are generated with respect to these. You can create all manner of rhythmic and stutter effects with this module, so I'm sure someone will love it.

XILS Lab SynthixNext to the LFOs lies the modulation matrix. This has six slots and allows you to route any of 29 sources to 38 destinations, all with positive or negative polarity. This is a huge step forward over the original synth. Elsewhere, the glide/portamento section has been enhanced with the addition of filter cutoff frequency as a destination. But if there's one place where I wish XILS Lab had deviated further from the Synthex (and didn't), it's in the way the joystick section is presented. The layout was clunky on the original, so it's a shame that it hasn't been updated here.

In an era when on-board effects were provided on low-cost, often single-oscillator synths in an effort to thicken their sounds, the Synthex was perhaps best known for its three-mode chorus unit, allowing its patches to sound more lush than those of Prophets, Jupiters and the like. This principle has been extended on Synthix, which boasts a multi-mode chorus that XILS Lab claim is capable of emulating the Synthex's, plus a delay line, phaser, and dual-band EQ. These are undeniably very useful but, like most digital imitations of analogue effects, exhibit little of the 'whoosh' associated with their vintage equivalents.

Voice Management

XILS Lab Synthix

Synthix scores over the Synthex in the number of voices it can produce (16 rather than eight) and the ways in which you can assign them. Firstly, it allows you to set up two parts, split and/or layered, and offers independent MIDI control of each. You can choose between a selection of poly and mono modes for each part and decide which voices will be assigned to each and (in the case of poly mode) how they are cycled. You can also set whether unison is used on either or both parts and, if so, with how many voices. Finally, you can set up the flexible arpeggiators (see 'The Arpeggiators' box) on each.

Glide controls. Glide controls. However, these are the only things you can do here; you're setting up two virtual keyboards, but both access the same patch. To make Synthix multitimbral, you press the MORE button, at which point eight boxes appear. These represent voices 1 and 9, 2 and 10, 3 and 11, and so on, and allow you to edit the sounds produced by each pair. Used with the Guitar mode (see 'Guitar Mode' box) this can turn Synthix into an up to eight-part multitimbral synth, although with just two voices for each. Programming and keeping track of everything is a bit of a nightmare, but it can be done, and you can create MIDI stacks as well as conventional multitimbral setups, although I suspect its most common use will be to create the underlying sounds used by the sequencer.

Joystick control.Joystick control.Ah yes... the sequencer. Like the Synthex's, this offers four monophonic parts and forces you to think in a late-1970s sort of way. While experimenting for this review, I created a two-step sequence with three patches — a bass sound, a resonant filter-sweep and a drone — and then applied echo and the phaser to the result. This led to all manner of extended effects, and I then played conventional melodies over this. The result was instant Tangerine Dream in their Rubicon era, and a bit of tweaking then saw me heading toward Blade Runner, which can never be a bad thing. You'd be better served using a modern sequencer/synth such as Reason for longer and more complex sequences, and for me, it's working within Synthix's limitations and overcoming them that leads to the most interesting results.

In Use

Voice Management controls. Voice Management controls.

Like many soft synths before it, Synthix combines the concepts and sound of its inspiration with facilities that would have been impossible or impractical when the original was manufactured. This means that it's not a clone; it simply claims to have the same character as the original. Whether or not that's true (I don't have a Synthex here to make a direct comparison), it's capable of producing sounds of great depth and power. Excellent brass and string pads, melodic leads and bass patches leap out almost unbidden, and when you start to use velocity and aftertouch, program the modulation matrix and add effects, it really comes alive. Putting everything under MIDI control is also simple, and I quickly assigned the knobs and sliders of an Arturia Analogue Experience Laboratory keyboard to adjust all manner of parameters, both for programming and for real-time tweaking, with remarkably smooth results.

For many people, the ability to layer sounds will be an important aspect of Synthix, but this is where things become less than straightforward. You have to assign which voices are available to which layer, and keep track of all of the edits within them. What's more, if you adjust any parameters in this mode, you can't return to the monotimbral 16-voice mode except by selecting a different patch. I had already decided I probably wouldn't use Synthix in this fashion, and then I started to experiment with the sequencer, at which point I decided I probably would. And therein lies the secret of Synthix; unlike many soft synths, it will give of its best only if you spend some time with it.

The 'More' button accesses multitimbrality. The 'More' button accesses multitimbrality. Unfortunately, it seems a little unfinished to me. For example, some of the legends are less clear than one would expect, some of the smaller controls have no legends at all, and many of the sources and destination names in the drop-down menus don't fit into the windows provided. Likewise, the documentation feels unfinished; some of the English (while a million times better than my French) is less than fluent, and there are a few inconsistencies between the GUI and the explanations in the manual.

Furthermore, programming is occasionally confusing. For example, when one of my patches refused to make a sound, it took me a while to find out that when you route key velocity to the VCA level and set the amount to zero percent, the result is silence. Once I discovered this, I realised that the modulation value and modulation amount are applied to the destination as a multiplying factor, rather than by adding or subtracting from an existing value, as is usual. XILS Lab agreed with me that the existing system is not ideal, and undertook to investigate it. In the meantime, this architecture means that you might have to be more careful with some of your patch programming than would otherwise be necessary.

Synthix's four-track sequencer. Synthix's four-track sequencer. Finally, I should note that Synthix currently imitates the inconsistencies and instabilities of analogue oscillators by applying fixed phase differences (on a voice-by-voice basis) between Osc1 and Osc2. If the oscillators are not detuned or modulated, this can lead to phase cancellation and tonal differences between voices. Indeed, some voices can appear to lie an octave higher than the others when their fundamentals are severely attenuated by the phase error. The result can be a patch that goes 'dong-dong-ding, dong-dong-ding...' as you play, which is not nice. I have discussed this with XILS Lab. It transpires that they originally took the decision to code Synthix in this way to save the CPU power needed to maintain 16 free-running oscillators. Nonetheless, they will now see whether they can address the issue. I like manufacturers who respond positively to feedback; it bodes well for updates and future products.


In a world replete with 'soft' Minimoogs, ARP 2600s, Prophet 5s, Jupiter 8s and all the rest, XILS Lab have tended toward the obscure for inspiration. Is this because there's something special about synths such as the VCS3, the PolyKobol II and the Synthex, or is it because it's an obvious way to differentiate their soft synths from everyone else's? Clearly, it's both, and XILS Lab synths tend to offer sounds and facilities not available elsewhere. So while the Elka Synthex is not quite in the same class of oddness or obscurity as the other two, Synthix still offers something different from the norm. Despite a few niggles, there's a lot to like and, if you're prepared to spend the time and energy to burrow into its depths, something interesting and euphonic will certainly emerge.  

Guitar Mode

Synthix offers a Guitar Mode that allows you to assign each of six MIDI channels to either one or a pair of voices, provided that you haven't assigned them elsewhere. I didn't test this facility myself — because long ago I gave the human race a break by removing the MIDI converter from my guitar — but I have no reason to believe that it would not work. Bear in mind, however, that, like Upper and Lower, this is not of itself a multitimbral facility, so each string will produce the same sound unless you invoke Synthix's 'More' mode of programming.

The Arpeggiators

The dual arpeggiators (one in the Upper and one in the Lower part) offer up, down, up/down and random modes, monophonic and polyphonic modes, and controls for gate time, rate and swing, all of which is good news. They offer one to three octave ranges, allow you to create a voice assignation order, and in poly mode they offer the rather interesting feature of allowing you to determine a chord sequence (well... to be more precise, a transposition sequence) of up to 32 steps, which can lead to some interesting and unusual results.

A Brief History

Italian manufacturers better known for their home organs, Elka produced some of the nastiest synthesizers of the late '70s and early-to-mid '80s. Yet amongst these were some surprising gems. The Rhapsody 490 was a lovely little string synth, and the Rhapsody 610 (while not sounding quite as nice) was used by many of the biggest names of the 1970s. Then there were the company's stage organs, such as the X109, the X605 and the mighty X705, the last of which combined organ, strings, percussive sounds and a basic monosynth in a monstrously heavy, dual-manual case. Played though an Elkatone rotary speaker, this was a fine instrument.

Released in 1982, the Synthex was the company's attempt to address the market for large, serious, polyphonic synthesizers. Few musicians ever touched one, let alone played one and, compared with its contemporaries — the Prophet 5, OBXa and Jupiter 8 — it was not highly rated. After a short life in which its price tumbled from £3199 to just £999, it was swept away by FM synthesizers and the low-cost analogue/digital hybrids of the mid-1980s. Why was it such a turkey? Did Elka's reputation work against it, or was there something fundamentally unsatisfactory about it? In truth, the problem was probably a combination of bad timing and the inability of the company to convince the world that they had produced a top-quality polysynth.

General Music bought Elka in 1988, and the brand name disappeared a few years later.


  • The basic voicing is very flexible.
  • It's capable of complex, evolving sounds, as well as powerful, bread-and-butter analogue emulation.
  • The sound quality is excellent.


  • Introducing fixed phase errors is not a good way to mimic analogue oscillators.
  • Advanced programming can be unintuitive.
  • The GUI and documentation feel a bit unfinished.
  • There's no stand-alone version.


The unusual architecture and combination of features in Synthix means that it's distinguishable from many other soft synths. If you're after something with the character of the Elka Synthex, you're not going to find it easy to obtain the original, so Synthix may represent your best, if not your only option.


€169 including VAT.

Test Spec

Synthix is not available as a stand-alone application. I installed it quickly and easily and ran the AU version without problems in Plogue Bidule. The VST version ran in Digital Performer 7 but, for reasons that I never uncovered, Bidule was unable to recognise the VST version.

  • Apple MacBook Pro, 2.6GHz Core 2 Duo, 4GB RAM, Mac OS 10.6.8.
  • Synthix v 1.01.
  • Plogue Bidule v0.9717 and DP v7.24.
Published February 2012