One of the big announcements from NAMM 2018 was the arrival of Korg’s Prologue polysynth, offering a new spin on analogue. Dave Gale investigates…
Price £1299 8 Voice | £1739 16 Voice
Prologue key features:
- Fully programmable analogue polysynth
- Professional grade full size keybed
- 8 or 16 voice versions available
- High quality FX section built-in
- Very stylish finish in aluminium and wood
- Onboard arpeggiator, offering numerous settings
- Open Application Programming Interface (API) for user created waveforms and FX
- Bi-timbral; layer and split
So here it is! The one we’ve been hoping and waiting for! A full size analogue polysynth from Korg, following their tremendous form over the last couple of years, with their various entry level synths and the Volca range.
Enter the Prologue, which as the name suggests, boasts something on a slightly grander scale, and with the design ethic that Korg have come to be recognised for. The Prologue is available in either an 8 or 16 voice form, with the 8 voice offering a 4 octave, full sized keybed, while the 16 voice offers an additional octave, taking it to five.
The keyboard is highly playable and velocity sensitive, with no aftertouch, but with a perfect synth action which is quick, but ever so slightly dampened in response. The handsome wooden end cheeks straddle each end of the keybed, and herein might lie a small issue for those who choose to gig with this keyboard.
The top and bottom C’s are a little exposed, which is slightly reminiscent of the vintage Arp Odyssey design, and in common with the early Odyssey, may well be prone to getting knocked or caught as it goes in and out of a case or box. Don’t get me wrong, it looks stunning, but I get the sense that the exposed end notes might be asking for trouble if gigged with regularly.
Sharing design aesthetics with it’s cost effective siblings, the control panel sweeps away in a little arc, with what feels like a beautifully engineered black front panel. There is no hint of pot wobble here, merely an oozing sense of quality, which invites the user in from the outset, to dial in and tweak at will.
The pots have a lined indentation on top, to indicate pot position, making it very easy to see its exact location. Pitch and Mod wheels are placed on the left of the panel, just above the keybed, and while fine, they don’t quite offer the same quality as the rest of the adorned fascia.
There’s a tiny bit of lateral movement here, but you only really sense this because of the excellence found elsewhere. Around the back, MIDI is available via conventional MIDI sockets and USB, while there is also Sync I/O on mini-jacks, to play nicely with Volcas or modular. You’ll also find a built-in power supply and pair of 1/4” audio outs; this is an analogue beast, and it’s in stereo!
Powering on, patience is the order of the day. The main thrust of this synth is its’ analogue circuitry, and you’ll have to wait 30 seconds or so for the Prologue to tune its oscillators. Once done, the first preset that invites a play is ‘Running Brass’. You’ll not need to try too hard to guess what may have inspired this, and as I would later discover, the Prologue shares a small sonic stamp with the likes of the Yamaha CS-80.
It’s always good fun to trawl through the presets, and when something strange takes your fancy, reverse engineer the patch to see how it was done. With 250 factory patches available, and a further 250 spaces for user patches, there’s plenty to inspire you, straight out of the box. The factory patches are nicely put together and give a good overview of what’s to follow, but the fun really starts when you start to dig into the architecture.
Subtractive time again
The main building blocks of the Prologue are three oscillators, with all located to the left of the front panel. VCOs 1 and 2 are identical, offering a choice of Saw, Triangle and Square wave. All of these can be further altered via use of the Shape pot, which changes the cycle or complexity of the waveform. This is a particular coup, as it places the Prologue in a different bracket to the more traditional vintage poly, which would rarely allow for this degree of control. The emanating sonic structures that can be produced at this stage are in themselves pretty inspiring.
Even the subtlety of a triangle wave can simply and effectively be mangled into something more metallic in construct, with the resulting sum being displayed on the Prologue’s rather sharp display, which serves as both an Oscilloscope and a handy read-out to confirm settings. Both VCOs offer a four-step octave control, alongside a fully sweepable pitch control.
Beginning my experimentations with just these two VCOs brings an added dimension of interplay into sharp focus with the addition of the modulation possibilities, which are immediately available from the front panel.
The Cross Modulation presents itself first; beginning subtly, the resulting rev-like sound of each increasing VCO beating against itself is terrific. You’ll also find Sync and Ring Mod available here, with the former possibly sounding a little tame, if compared to the more ubiquitous sync-tones of the classic American synths, but the inclusion of the Ring Mod more than makes up for any shortfall.
This is the gnarliest of the mod-lot, and at this point I have to mention the wave shape control again, as this can really mix things up into an absolute sonic powerhouse. Play around with the shape of the modulating VCO and you’ll be transfixed for hours. It’s fair to say that if you find yourself lost in a single section of a synth, as I did working with just the two VCOs, it’s a great sign of an inspiring synth.
Moving to the third Oscillator, which is described on the front panel as Multi Engine, it is unsurprisingly somewhat multi-faceted. In its most simplistic mode, Noise delivers four noise-based timbre, while the Shape pot will control facets such as filtering.
A big favourite here is the Decim timbre, which offers sample rate reduction, and will immediately inspire if adding crunch to percussive patches. The next mode of operation is VPM (Variable Phrase Modulation), and was apparently developed specifically for the Prologue.
In reality, it’s similar to a basic FM synth construct, offering a single carrier and modulator, with the resulting tones being quite reminiscent of some of the more basic DX tones produced in the late 80s. Regardless, they are interesting and useable, largely thanks to the ever-present Shape control, which will increase the rate of modulation, creating sharp and often metallic overtones.
The final aspect of this third oscillator could possibly be the most exciting and enticing, as it will allow the user to upload and save up to 16 of their own oscillator programs for inclusion in synth patches. Creation of these tones will be via Korg’s own free software, which was regrettably unavailable at the time of writing this review.
The Prologue does, however, ship with a single wave onboard, but there is no doubt that this is an area for further exploration, which will allow the user to continually update and grow creatively, refreshing the oscillator with new waves, over time.
All three of the oscillators feed directly into a simple three fader mixer right next door, before entering the filter section, but I cannot leave the Oscillator section without referring to the Voice mode section, which will also play a heavy role in dictating the VCO sound.
As seen before on the Minilogue, there is a choice of four voice modes: Poly, Mono, Unison and Chord. These largely speak for themselves. It’s difficult to resist switching to Unison mode and stacking up 32 VCOs, just because you can, but it’s the lure of the Voice Depth and Spread controls here that will excite most of us.
The Spread pot will space out the VCOs across the stereo spectrum, resulting in an absolutely gargantuan fest of space, with detuning effected by the Voice depth. Moreover, coming back to the favoured Shape control, sub-tones appear with such ease that it’ll have the ground beneath you shaking in a heartbeat.
It’s important to remember that 2/3rds of the oscillator section is analogue-based, with the Multi Engine making up the final digital 1/3rd. This means that you’re getting the best of both worlds, but you’ll also be getting the detuning potential of an analogue synth.
I did find VCO tuning drift within the first 20 minutes of usage, after switch-on, but further manual tuning of the oscillators resulted in a very reliable machine. Given the importance of the ability to retune the VCOs, I found it a little odd that the button press for this is not very obvious, requiring a flick through the manual and the press of two buttons simultaneously, but it is nevertheless possible to perform.
Do I really need this?
The notion that you might need a polysynth is very debatable, given the strength of many software equivalents at a fraction of the price. It could be regarded as a generational thing, as people of a certain age grew up listening to and playing polysynths. However, the allure of a polysynth will probably have more to do with how you intend to use it.
If you play live, and need the ability to play polyphonically, this is a great synth to consider, but when you also add the concept that it’s something of an analogue synth for the next generation, you’ll find it hard to ignore the creative side of what the Prologue can do, and I found myself being drawn in to use it. It’s a player’s synth, but it’ll be very at home in the studio.
After the creativity of the oscillator section, next up is the Filter. With a centrally located Cut Off pot, which is also slightly larger, the filter is a fixed 2-pole design offering Low Pass, with the usual resonance and key-tracking. Being 2-pole, it is particularly crunchy, but with a great degree of pot resolution.
It sounds crisp and characterful. Despite this, I found the resonance to be quite quick in feeding back, but when backed off slightly, there’s a beautiful wispiness to the top end which is a little reminiscent of the Polivoks-based design. Key-tracking is applied in amounts of 0, 50% or 100% via a switch.
There is a degree of low-end reduction, as resonance is applied, but Korg are way ahead of us here, as they have included a drive switch, which will apply distortion in steps of 0, 50% or 100%. This effect perfectly places the low-end tone back into play while it messes beautifully with those high end resonances, to give even more character to the top end.
There is a lack of a sweepable High Pass Filter, but there is at least a simple switch, which will deliver a basic HPF roll off, and defeat any thuds that might be heard in the bottom end, which is particularly useful when the Drive is in play.
Two full ADSR envelopes are on offer, with one immediately assigned to the filter section, but also offering duties elsewhere, such as the ability to control the pitch of the VCOs. One shame is that it doesn’t appear to be possible to route the envelopes to many other locations, but it is possible to invert the envelope phase.
The LFO, on the other hand, can be directed to a number of modulation locations, including the oscillator shape, and can be easily clocked to a given signal, while offering Saw, Triangle and Square waveforms. The most useful elements of assignment are immediately available from the front panel, while delving into the Prologue’s menu system will allow for a greater degree of assignment options.
FX, Compression and stacking
There’s an extensive set of high quality effects available on the backend of the Prologue, with an independent Delay/Reverb section, and a further Modulation section, which include Ensemble and Chorus type effects.
The thickening of these Mod effects is pretty good and they can be placed in such a way that they are not obvious, but may not always be required, given the generosity of the upfront tonal construct. I did find some of the reverberations to be perhaps a little too bright and resonant, but thankfully there is plenty of options to choose from, with 10 reverb types available, accessed via the Prologue’s menu system.
One unique feature to the 16 voice Prologue, which is not available to the 8 voice, is the inclusion of a backend compressor. Apart from offering a degree of VU meter eye-candy, the compressor will helpfully both compress and replace some of the low-end frequencies that may be lost along the patch building way. It’s obvious when it kicks in, but can also be utilised subtly, thanks to the inclusion of a gain control. The Prologue also boasts the ability to layer and split the keyboard.
In this mode, the overall polyphony will halve, but the result will be the ability to place one timbre alongside another on the keyboard, or stack two timbre for an even greater depth of sonic character. In this mode, it is also possible to seamlessly crossfade from one timbre to the other, but if this is something that draws you in, the extended polyphony of the 16 voice Prologue will clearly be worthwhile, as the voice count will reduce to 8 in this mode, rather than 4 on the 8 voice model.
The overarching point that I will take away from my time with the Prologue is that it is a really enjoyable synth to use. I cannot overstate how easy the front panel is to work with, as it draws you in both aesthetically and creatively. I absolutely love the complexity of the oscillator section.
This, for me, is the absolute nerve centre of Prologue action, and once the SDK software is available, is going to further extend an already boastful creative centre. It is a real synth player’s keyboard, and will be used by many as such, while the addition of an arpeggiator, with easy clocking functions to other Korg products such as Volca’s, make for a great Korg eco-structure, albeit one that is really well built and should provide plenty of sonic creativity
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