Review – PolyKB III by XILS-lab

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A powerful synth plugin has just been improved, with a better layout and more modulation possibilities. Our reviewer checks out what’s new in this major update.


by Rob Mitchell, Mar. 2017


XILS-lab is known for their high quality music software, which mainly focuses on the recreation of vintage synthesizers. PolyKB III is the latest version of their RSF PolyKobol synthesizer emulation. The original hardware synthesizer was a very rare item, as only 30 were built by the original company.

For this review, I will mainly focus on the emulation’s newer features. If you’d like some more details on the PolyKB II, you can read my July 2015 review of it here:

For the PC, PolyKB III works with Windows XP or later, and in the following formats: VST, RTAS, and AAX (Pro Tools 7 and later).  For the Mac, it works with OS X 10.7 or later, and in the following formats: VST, Audio Unit, RTAS, and AAX (Pro Tools 10 and later). PolyKB III is Native Instruments NKS compatible. At the moment, a standalone version is not available.   Both 32-bit and 64-bit compatibility is supported.


 Oscillators and Filters

The original PolyKB II was a two-oscillator subtractive synth plugin. With the latest and greatest PolyKB III, there are now three oscillators. They are all identical, and each of them can morph between the waveforms.  These include Triangle, Saw, Double Saw, Square, and Pulse, or anywhere in-between. The second oscillator can be set to “Low”, which lets it act as an additional LFO.

Besides having a third oscillator, it also offers a second filter and an associated envelope. These are both 0df (zero delay feedback) filters, and this results in a very smooth response that’s very close to analog in its character. These two filters can be setup in series or parallel. Along with the second filter, they’ve also added new band-pass and high-pass modes. Drive is available for each filter, and this can be used either pre-filter or post-filter. For each filter, you’re able to select which VCO and/or Noise will be fed to whichever filter. So you can have (for instance) VCO 1 and VCO 2 routed to the first filter, while VCO 3 and Noise are routed to the second filter. They’ve also added a control in the lower-right for you to mix the levels of the two filters.


Effects and Modulation

With the newly revamped interface, everything has been given more room, and that includes the Effects section. I really like being able to see all of them at once since with PolyKB II you had to switch between tabbed views to jump to another effect.  The effects include a Delay, Phaser, Chorus, and EQ. As far as I know, there were no changes to the effects since PolyKB II was released. That is fine though, as I thought they were all more than adequate.

With this new version, you’re able to switch between several different views. In PolyKB II, the overall display was very “busy”, and it was a little confusing. Now you can select from the separate functions by using a slider at the far left. This gives the controls more real estate on the screen, and (for me) it really helps me with the workflow. I think this is a big improvement, and it’s just plain easier on the eyes as well.

Using the slider to change the view, you can switch between the Sequencer, Voice XY, Space XY, Arpeggiator, Wired Modulation, User Modulation, and Effects. The Sequence section now has a feature allowing you to separate the voices from the Sequencer, and lets you use them as a modulation source.  The Wired Modulation section now has VCO 3 added, and the second filter is available in both the Monomod and Polymod sections.

The way to use the new Sequencer functionality is within the User Modulation section. After you have setup your sequence the way you’d like, you just switch over to the User Modulation view using the slider. From there, you can use the new sources that are available under the “Modulators” category. There are four separate sequence pitch tracks that are labeled as SqNot1, SqNot2, SqNot3, and SqNot4. These sources can be used for modulating a variety of destinations. For example, the first track of the sequence could be configured to affect any of the three oscillator’s tunings, waveform settings, and/or level settings. The next track could affect the filter’s frequency, resonance, and/or drive. In total, there are four destinations for every source. Even if you just used one track, it could affect oscillator tuning, filter cutoff, a stage in an envelope (A/D/S/R), plus either one of the LFOs, and/or the Delay’s settings.

Besides the whole modulation section being easier to read and spread out on the screen, the Sequencer display (where the notes are displayed) has also been enlarged. Here is a screenshot showing the difference between the PolyKB II version on the left, and the latest PolyKB III version on the right:


Also, when you click on the magnifying glass icon to enlarge the window, it is now much easier to view it. Here is that screen, with the PolyKB II version on the left, and PolyKB III on the right:



This was already a great synth plugin, and with the many added improvements its capabilities have been boosted even further.  One thing I wanted to touch on was that the additional functions for the envelopes are very handy, letting you loop the envelopes for ADSR 2 and ADSR 3. The “Multiply” (MUL) function will multiply the settings of the envelopes by a factor of 2, 3 or 4 times the original amounts. These Loop and Multiply features were available in PolyKB II, but I thought I’d mention them again as there is now an additional ADSR envelope.

Lots of modulation options, an improved interface, a rich sound with awesome filters, and just the right amount of effects on board make this a very powerful synth plugin. PolyKB III is available for 159.00, which is about $170 USD. You can upgrade from PolyKB II for just €39.00 (~ $42 USD).  There is a demo version you can try, plus there’s more information on their website here:




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