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By Ken Hughes

Calling it "rare" is an egregious understatement. With build estimates at roughly 30 units, it was exceedingly rare to begin with. Add 27 years of attrition, and surviving RSF Polykobol II hardware synths are better described as “apocryphal.”

French coders XILS Lab have virtualized this footnote in synth history. Founder and chef de l’ingénierie Xavier Oudin told me that top among the challenges was re-creating one of the Polykobol’s defining features: Oscillator waveforms that are continuously variable from sawtooth to pulse. The wave morph can be modulated by velocity, LFO, envelope, etc., and to get it done in the digital domain without aliasing, zippering, or other artifacts is a tall order. One of the other unique and cool Polykobol features is the multi-waveform LFO; it can output any combination of its waveforms simultaneously, and they sum, producing a living, wriggling modulation from subtle to extreme.

Since I work primarily in Pro Tools, I got the RTAS version and dove in. I had trouble with the original release of PolyKB; running the large UI (because it’s freakin’ gorgeous) on a single stereo Instrument track with no other plug-ins or even tracks instantiated, my 2.14GHz Intel Core Duo iMac gagged on PolyKB’s more complex presets like a Texan trying sashimi. The machine is well within PolyKB’s stated system requirements, and I had my audio buffer set at 1,024 samples, twice the 512-sample minimum recommended by XILS. We contacted them and they suggested I run the smaller UI, citing word from a Windows user who had had similar trouble using the large UI. That solved the problem, but it was a bit of a daft workaround. I’m now happy to report that PolyKB II ran the large UI on both the desktop iMac and my MacBook (non-Pro) without problems. The AudioUnit version worked great in Logic and GarageBand on both machines.

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Alias-free waveform morphing is computationally intensive; there’s a deluge of math problems to be solved every time the waveform generates harmonics that aren’t evenly divisible or multipliable by your project’s sample rate. This is why if you pile on heavy automation (every synth parameter in PolyKB II is available to the host), you’ll need a stout machine. Both of my modest machines could support a reasonable real-world amount of automation, but getting mental with it choked both Macs. But what fun!

La Voix (The Voice)
About that sound. Because no hardware Polykobol has ever crossed my path, I can’t make direct comparisons between the plug and its silicon-and-wood counterpart. Only a handful of people on the planet could: Hans Zimmer, Vince Clarke, Jean Michel Jarre. . . . Truly, because so few of us have ever even seen or heard a Polykobol, total authenticity is kind of irrelevant. What matters most is whether PolyKB II gives us anything the other virtual analog synths (hardware or software) don’t.

It most certainly does. Timbre-wise, it’s hard to overstate the unique possibilities offered by the two most obvious Polykobol quirks: the variable-wave oscillators and the multi-wave LFOs. XILS has succeeded in giving us alias-free morphing oscillators. That the waveform can be modulated by velocity, LFO, and envelope 2 is remarkable. Sure—hard oscillator sync, when the frequency of one of the oscillators is modulated, does give you an output waveform that changes over time. Many synths can do that, but this is different and it sounds different.

The filter is excellent. Wicked resonance is available, going well into speaker-frying territory. PolyKB II, ironically enough, gives up an acidic TB-303 sound that a real 303 only wishes it could achieve. Filter overdrive is available in abundance and can be switched pre- or post-filter for two subtly different textures. If you like to get rude, PolyKB wants to be your Charlie Sheen; aggressive, but nuanced and captivating rather than just crudely abrasive. On the flipside, the filter is capable of smooth lushness for fantastically dark yet articulate pads. Try overdriving the filter hard and then closing it down to get an unsettling dark timbre. It’s alive.

The additive LFOs (my term) are delightfully quirky. Multi-wave LFOs aren’t uncommon, but one capable of outputting all available waves simultaneously—and interactively—is a wondrously off-kilter design element, and PolyKB II has two of them. Leave it to the French. . . . Many of PolyKB II’s presets use the built-in sequencer, but during my initial once-through, I disengaged the sequencer on one of the presets. The patch continued to burble and squirm, both in pitch and in timbre, in a way I couldn’t attribute to traditional LFO—it was aperiodic, yet symmetrical. What in the wide, wide world of sports is a-goin’ on here? If you stack multiple waves on the LFO, they create a bizarre aggregate wave that sounds pretty darned unique. Imagine the effects you could create with that: from the lugubrious to the manic, the tastefully subtle to the profanely overt. Both LFOs also offer Delay and Fade controls, which let you delay the onset of the LFO and then fade it in at the rate you set.

Modulation in PolyKB II is extensive, and here’s where XILS’ faithfulness to the original is either charming or confounding. I kind of enjoyed the initial befuddlement factor, as it encouraged experimentation and took me places I probably wouldn’t have gone had the synth layout been more “normal.” There are two pages to the modulation section, denoted by the brackets around the panel legend (any parameter with a bracketed label hides a second page); click the label and you get one of two identical-looking pages. What? XILS gives you the choice of the plug-in’s version 1 modulation section or a new improved version. Toggling back and forth with a sequence running revealed subtle but real differences in an otherwise identical patch.

In addition to the hardwired sources and destinations, there’s another section of controls that are completely configurable. Sources available include both envelopes, velocity, aftertouch, keyboard tracking, both LFOs, sequencer pitch and velocity, the modulation wheel, and “LFO1 and 2 M.”

Step Sequencer
PolyKB II offers an eight-track sequencer with a maximum of 32 steps. Things get more delightfully bizarre here. This is a 16-voice synth, and you can select how many of the voices are modulated by the sequencer. So you can get any combination of notes that follow your fingers and notes that follow the sequencer. It’s devilishly difficult to describe this in words, but the end result is patches that sound like a whole lotta stuff going on when all you’re doing is holding a note. One example: In mono keyboard modes, careful legato playing will keep the tonal center of the sequence rooted to the first note you play; subsequent notes will play the non-sequenced voices and change the note underlying the sequence—with or without portamento.

Sequences can be recorded in either real time or in step mode. I’d like to see a simple metronome click in the plug-in itself for recording, but you can always run your DAW’s click. Velocity can be recorded or ignored, your choice. Sequences can also be saved independently of their associated sound presets, letting you build up a library of sequences.

A piano-roll editor is available by clicking on a tiny “+” icon at the bottom right corner of the sequencer window; clicking a yellow magnifying glass opens a pop-up larger version. The default screen is an “all available values” view (measured in percentages) that underscores the sequencer’s value as a modulation source as well as a microcompositional tool.

There’s a whole bank of factory presets dedicated to sequenced effects, and many of them sound like they could be dropped wholesale (and solo) into film, TV, and video game soundtracks. Of course, no composer worth their salt (unless on a deadline of “yesterday”) would use them naked, but they’re that good.

DynaMYX and PolyMYX
These features are quirky in the extreme, fascinating, and jaw-droppingly cool. DynaMYX is a real-time spatial animation, er, thing. Imagine a multi-touch Korg Kaoss pad that lets you set each voice in motion across the left/right and close/far ranges, and you sort of have the visual. You don’t get to trace each voice’s trajectory as you wish, but there are two “behaviors” selectable and four amounts. You can also set the virtual mics’ static splay angle and their distance apart. Yeah, it’s nutty, but how does it sound? Different from stereo chorus or unison, obviously. It’s not reverb; it doesn’t “wet” the sound at all. Once you get the voices whirling around, it’s a vividly stereo effect. PolyMYX uses the same X/Y paradigm and applies it to up to four parameters, one at each corner. Although I can hear animation of the parameters in PolyMYX, the display doesn’t animate as in DynaMYX.

Zut alors! Le PolyKB II est très cool. Et tout en finesse. Sometimes the French sensibility escapes me, but this plug-in is exciting. There’s nothing else out there quite like it. Unique and different to be sure, but not so weird that you can’t also use it for more basic stuff like pads, bass lines, and leads. It’s actually a hell of an all-rounder. Key Buy? Mais bien sûr, mon ami.

Faithfully re-creates an extremely rare hardware synth. Unique timbre. Seamless waveform morphing. Cool sequencer.
What makes it unique and cool also makes it a little opaque at first. Can be CPU-intensive. No standalone version.

Up to 16 voices.
Mac: AU (Universal Binary), RTAS. Win: RTAS, VST.
Mac: OS 10.3.9 or later. Win: XP, Vista, or 7.
Both: 2GHz CPU, 1GB RAM, Pro
Tools 7.0 or later for RTAS use.

Fun and inspiring whether or not you care about the vintage emulation aspect. €49 direct (approx. $205 at press time)


Get original audio examples here.

Download the free demo.