Recording - April 2011 - 61

PolyKB II The PolyKobol was a polyphonic keyboard synthesizer from French analog synth maker RSF. It started from its monophonic predecessor the Kobol (beloved of Vangelis, Depeche Mode, and many others), and added a lot more than just polyphony. The PolyKobol was a very impressive synth, with hitherto-unknown waveform-morphing oscillators, a built-in sequencer, and even an onboard cassette tape data storage system. Only 32 of them were ever made, so please forgive my lack of comparisons between the plug-in and the real thing! The basic layout of the PolyKB II’s voice is simple: two oscillators (VCO 1 and 2) into a 4-pole lowpass filter with overdrive (VCF) and out through an effects processor with individually selectable delay, chorus, phaser, and eq (dual resonant shelving filters). The VCOs offer hard sync, a white noise generator with a band-limiting option to remove the highest frequencies, and keyboard defeat on VCO 2, but the standout feature here is the Waveform knob, which smoothly morphs each oscillator’s output waveform from triangle to sawtooth to double (rectified) sawtooth to square to pulse. This sort of waveform changing produces a very different sound than traditional pulsewidth modulation, and makes the PolyKB II sound very rich and powerful.

Audio Clip 3 illustrates manual sweeps of the Waveforms on both Oscillators as a polyphonic arpeggio plays back. The two ADSR envelopes are dedicated to the filter cutoff and output level, but they can be routed for use as general modulation sources. ADSR 2 can be set up to loop constantly through its attack, decay, and release, as long as a key is held down. The synth includes two LFOs with multiple waveforms; you can create complex modulation shapes by selecting several waves at once. There are three different modulation sections! One offers hardwired routings selectable with switches, one has user-definable routings via dropdown menus, and one uses an XY graphic display. This last section has two subpages, DynaMYX for dynamic voice movement in a simulated soundspace (complete with a movable “stereo mic array”) and PolyMYX for polyphonic modulation—each voice can have different mod amounts, depending where it’s placed in the display. The arpeggiator offers simple up, down, or up/down movement, with swing and gate time control and a chord-based polyphonic mode. The sequencer can play back data for up to eight voices, and is similar in many respects to the XILS 3’s. There’s a hidden piano-roll graphic sequence editor hidden under the “cassette panel”, which is also where you’ll find the DynaMYX/PolyMYX display and the extra arpeggio parameters.

There’s a lot going on under the hood, and it translates into very rich, evolving sounds. The combination of dynamic stereo movement, polyphonic modulation, and morphing waveforms means the PolyKB II simply doesn’t do “bland” or “static” unless you work very hard to make it that way. Again, this works to your advantage with respect to CPU load; my test system couldn’t handle more than 8 to 10 voices out of a possible 16 with a dense patch, but two to four voices is often plenty with this much going on. I found myself exploring single patches for hours on end, just playing with the many modulation possibilities and hearing how this supposedly simple architecture could sound endlessly complex and beautiful. Audio Clip 4 combines a polyphonic sequence, delay, some gentle eq, PolyMYX, DynaMYX, and manual Waveform sweeps. And all this with only three voices! Just as this issue went to press, XILS-lab announced PolyKB II Player, a very inexpensive version with a limited number of user controls but the same sound as the full version; see the website for details. Whether you’re in the mood for tweaky experimentation from the early 1970s or a rare and lovely analog sound from the 1980s, XILS-lab deserves your attention. Thumbs way up.

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Recording - April 2011

Table of Contents for the Digital Edition of Recording - April 2011