You are here

Sequential Trigon-6

Polyphonic Synthesizer By Gordon Reid
Published October 2023

Sequential Trigon-6

Dave Smith’s last synthesizer is a worthy farewell from a man who gave the synth world so much.

Sometimes living people feel constrained to write nice things about dead people for no reason other than that they’re dead. I’m not one of them. As far as I’m concerned, an old bugger who has died is just a dead old bugger. I’m telling you this so that you’ll have context when I say that Dave Smith — the founder of Sequential — was one of the nicest blokes you could ever meet. That he was also a brilliant engineer who gave the world some of its finest synthesizers and was instrumental in the creation of MIDI was just another facet of the man. So it was with huge regret that, having planned to meet him at NAMM last year, the first newsflash that I received when I landed at Santa Ana airport was to learn of his death. Never again would I have the opportunity to ask him when he was going to fix my Rev 1 Prophet 5, only for him to repeat our long‑time ritual of telling me, most politely, to get lost. I will miss him, as we all should. At the time of his death, Dave was working on the Trigon‑6, which was announced later in the year. Now described by Sequential as the company’s “polyphonic take on the classic, thick and creamy analogue sound that defined the dawn of the synth era”, I wonder whether it’s a fitting tribute to the man and his achievements. Let’s find out.

The Technology

Whether packaged as the original Trigon‑6 keyboard or the recently announced desktop module, the Trigon‑6 is a 6‑voice, monotimbral analogue polysynth based upon three oscillators and a ladder filter per voice. The former makes it unusual, because the majority of polysynths rely upon two oscillators per voice. Nonetheless, it’s clearly a member of a family that includes the Prophet 6 and the OB‑6 and, like its siblings, is based upon six voice cards inserted into a motherboard that provides common facilities and housekeeping functions.

Each of the three oscillators in a voice offers sawtooth, pulse and triangle waves, with an additional ramp wave on osc 3. With exception of osc 3’s mutually exclusive saw and ramp waves, you can select any combination of these that you wish. Each oscillator also offers five octave settings, with detune of up to ±7 semitones on osc 2 and osc 3, hard sync of osc 2 to osc 1, an LFO mode on osc 3, and the ability to disconnect osc 3 from the keyboard CV and MIDI notes. White noise is provided by a separate noise generator.

The output from each voice’s oscillator section passes via a mixer to its Moog‑inspired low‑pass, resonant ladder filter. This offers 12dB/oct and 24dB/oct modes and responds like many such filters from the 1970s; as you increase its resonance, it passes less and less of the low frequencies presented to its input, creating a quasi‑band‑pass response at high values. I have always favoured synths that retain their welly when the resonance is cranked up, but I know players who prefer this response, so I’ll leave it to you to judge whether it’s a good thing or not.

The filter will oscillate at maximum resonance in either mode, and will track the keyboard at 50 or 100 percent when asked to do so. With tracking of 100 percent it will — unless confused by enharmonic pitches — lock to the oscillators, so you can use it as a fourth chromatic oscillator. If there’s a shortcoming (and it’s a common one) it’s that the resolution of the cutoff frequency knob is quite coarse. This may not bother you, but it’s worth noting nonetheless.

Lying in the oscillator section, there’s a knob that I haven’t yet mentioned, which is labelled FDBK <> DRIVE. Turned clockwise from 12 o’clock, this increases the oscillators’ output to overdrive the filter input. When turned the other way, it routes each voice card’s output back into its filter input, thus replicating the trick that we all used to fatten up the Minimoog — but here done polyphonically on a voice‑by‑voice basis. The results can range from warmth to chaos — you choose.

The output from the filter passes through an amplifier before being presented to two 24‑bit/48kHz digital effects units. Effect A offers two sync’able delays, a chorus, three phasers including an emulation of the original Oberheim phaser, an emulation of the Oberheim ring modulator, and two flangers, while Effect B adds four reverb emulations to these. Each effect algorithm offers just two parameters, so it’s unlikely that any of them will replace your expensive studio devices when recording, but the programmed effects are stored on a patch‑by‑patch basis so, for sound design and live performance, they work well. Nevertheless, if you’re a fanatic, switching both effects off takes them and their associated A‑D and D‑A converters out of the signal path, so your sounds can stay in the analogue domain until they reach your digital mixer, or MP3 converter, or CD recorder, or are uploaded to YouTube... or whatever.

Shaping and modulation are grounded in the 1970s. The two contour generators — one dedicated to the filter cutoff frequency and the other to the audio signal amplifier — are conventional ADSRs. The global LFO generates six waveforms (yes, I know that only five are shown on the panel), offers eight destinations, can be sync’ed to master clock or MIDI, and can be key‑sync’ed if desired. Polyphonic modulation is generated by a Polymod section similar to the one that helped define the Prophet 5, but now with seven destinations rather than three. It was a powerful system 45 years ago, and it still is. Unfortunately, you can’t tune osc 3 perfectly to either osc 1 or osc 2, so it’s impossible to obtain consistent 2‑op FM sounds. In addition, the maximum depth may be too shallow if you want to stray into the realms of sonic mayhem. You can do a lot with Polymod, but perhaps not everything that you might imagine.

The Trigon‑6 measures 807 x 323 x 117mm and weighs 9.5kg, which in polysynth terms is more or less bantamweight.The Trigon‑6 measures 807 x 323 x 117mm and weighs 9.5kg, which in polysynth terms is more or less bantamweight.

For such a simple‑looking synth, the Trigon‑6 offers a wealth of additional voicing capabilities including a powerful unison mode and chord memory. When played with your choice of key assignment (low, high or last note with single‑ or multi‑triggering) and glide mode (polyphonic or legato, either fixed rate or fixed time), this makes it a powerful and very flexible monosynth. There’s also a clock section that can generate master clock or sync to MIDI, and this drives the Trigon‑6’s arpeggiator and step sequencer, the outputs from which can be transmitted via MIDI to other devices such as synths and DAWs.

The sequencer offers 64 steps (including rests and ties if desired), each of which can be up to six‑note polyphonic, and the results are stored as part of the current patch. Programming it couldn’t be simpler and, if you have enough voices, you can play over the top of it. If you replay any sequence (whether recorded as monophonic or polyphonic) in unison mode, it’s reduced to a monophonic line and playing keys transposes it rather than adding additional notes, which is always welcome. But remember that there’s no multitimbrality here; every note, however generated, produces the same sound.

Finally, there’s an analogue distortion unit, a Vintage knob that applies offsets to the oscillators, filters and contour generators to make everything sound ghastly (or interesting, depending upon your perspective), 63 memories for alternative tunings, mono and stereo modes, pan spreading to create a stereo soundstage when multiple notes are played, and a patch volume control so that you can balance each sound against the rest.

Having Fun

I unboxed the Trigon‑6 keyboard as would any new owner, and was dismayed to hear a metallic sliding noise as I removed it from its packaging. This was repeated when I rocked the synth from side to side. Clearly, something had come loose, and there was no way that I was sticking a mains cable into the back until I had fixed it. I don’t like to attack other people’s gear with screwdrivers, but removing a couple of screws at each end released the cheeks, and removing another four allowed me to flip open the control panel to locate the offending object. This turned out to be one of the four retaining screws for the internal power supply. The PSU itself was still held firmly in place, but the loose one could have created a short, so I returned it to its hole, and all was well.

I ran the auto‑tuning routine before starting my tests because it was obvious that, out of the box, the six voices were quite different from one another. I then ran it again, and again, and again. Each application brought the synth closer to correct calibration — not to the point of being boring, but to the point where every note in a chord sounded like it belonged there. I then made sure that the synth was in Live Panel mode and was finally ready to program and play.

One of the key tests of an analogue synth is whether a single oscillator can sound interesting; if you need two detuned oscillators to achieve anything desirable, you’re probably playing the wrong synth. The Trigon‑6 passed this test with flying colours; a single overdriven sawtooth wave or a pulse wave with just a tad of PWM can sound lovely. Outputting multiple waveforms from a single oscillator adds depth and, with just a tiny amount of Vintage dialled in, invoking two or three oscillators per note can sound monster.

The combination of three oscillators and a ladder filter per voice seems to have caused a section of the synthisphere (did I just invent a word?) to become obsessed with discovering whether the Trigon‑6 can emulate the Memorymoog. So I conducted some further tests with various oscillator, drive and filter settings, and the results were as meaningless as I had expected them to be. Program a simple patch ‘just so’ on both, and the sound will of course be similar. But push things further and they are distinctly different instruments. At one end of the scale, the Moog will create that “I don’t care what else is going on, listen to me!” for which it’s famous. At the other end, the Trigon‑6 sits more comfortably in sweeter, more mixable Prophet‑y territories. But if I’m honest, I think the question is pointless. I love my Memorymoog, but I sometimes feel that I have spent more time bending over it with a mirror to get it to ‘TUNE 6’ than I have playing it. Having done so, I then find myself moaning about its noisy cooling fan and worrying about the day when it takes up smoking. So let’s be practical. If you want a three‑osc/voice analogue sound in 2023, you could carry a large, heavy, fragile and stupidly valuable Memorymoog around and produce a glorious Moog‑y sound. Alternatively, you could take an even larger and heavier Moog One and produce a much wider and more complex range of even gloriouser Moog‑y sounds. Or you could take a Trigon‑6. Would any of these produce the precise sounds that you want? How can I know? But, other than for a permanent installation, I would probably choose the Trigon‑6 every time. Mind you, I would add a six‑octave MIDI controller to the setup...

Let’s talk about the Trigon‑6’s keyboard. This generates velocity, although you can only direct it to two internal destinations — the amounts of the filter and amplifier contours. It also generates channel aftertouch that you can direct simultaneously to your choice of eight destinations. With eight velocity curves and four aftertouch curves, I quickly found a combination that suited me, and I spent many happy hours recreating expressive sounds from vintage synths such as ARP ProSoloists, and doing more modern things such as introducing and increasing the depth of effects by pressing a bit harder. So far, so good. But let’s now talk about the keyboard’s width and feel. My dislike of four‑octave keyboards on polysynths has been stated in these pages before, not least when I reviewed the Prophet 6 (SOS November 2015). And, while I realise that Sequential’s ‘6’ series synths are all based upon the same hardware design, what they have done here is install a Rolls Royce Merlin engine into a Ford Focus chassis. Yes, I understand all the arguments regarding small studios, lightness, portability and so on but, if you want to get the best from the Trigon‑6, you’re going to need a wider keyboard with a more expensive feel. Four octaves with a light, springy touch are fine for a monosynth but, unless you’re going to spend your life playing pads in triads, it’s not enough for a polysynth.

Happily, I found the build quality of the Trigon‑6 to be excellent, and I love the maple chosen for the case. If I have to find fault, it’s with the continuing use of a three‑character LED display rather than a modern OLED that could fit the same space. I have no problem with this when programming, but it’s a pain in the backside when recalling sounds. If you like to get your hands dirty by programming and saving your own patches, you’ll soon end up with scraps of paper scattered all around the synth to tell you which sound is which and what it does in which composition. In this regard, it’s time for Sequential to move on. That reminds me... There are 500 factory patches duplicated in memories 000 to 499 (all of which can be overwritten) and in memories 500 to 999 (none of which can). Some of the factory sounds are very good, and I imagine that many players will use these as supplied or with just minimal tweaking. But where’s the fun in that?

From gentle orchestral‑style accompaniments to the most powerful leads and basses, it’s all there to be discovered.

Despite these shortcomings, I like the Trigon‑6 very much. There’s nothing here that you haven’t heard before but, depending upon how you program things such as the initial oscillator levels and the drive/feedback, it can be gentle, it can be warm, it can be crunchy, it can be aggressive, and it can even be downright violent. I programmed some pads that took me straight back to 1978, some sequences that reeked of the 1980s, and a whole range of polyphonic patches that brought me right up to the present day. The Trigon‑6 also excels as a monosynth, producing sounds that would grace any recording. From gentle orchestral‑style accompaniments to the most powerful leads and basses, it’s all there to be discovered. And, when experimenting with the Polymod section and applying high levels of feedback, I created sounds and effects that would have enhanced any sci‑fi movie from the 1950s. To be fair, the lack of consistent 2‑op analogue FM (or ‘cross‑mod’) is a disappointment, and harsh clipping can occur if you push things too far but, for me, the Trigon‑6 never sounded lifeless or boring, and that’s no small compliment.


Many years ago, a series of television adverts used the tag line, “One Instinctively Knows When Something Is Right,” and so it is with the Trigon‑6. I was playing factory sounds that I liked very much within moments of switching it on, and soon I was programming new ones that I liked even more. Inevitably, it won’t be for everyone, but there are many players for whom it could be an ideal synth. Despite a couple of limitations, it’s capable of sounds ranging from beautiful, ethereal pads to screaming excesses, covering a huge range of ground between, and doing so with an ease and quality that belies its diminutive stature. I hope that Dave would have been pleased by it. Indeed, if you’ll forgive my presumption, I think that he would.

The Rear Panel

Sequential Trigon-6

As befits a monotimbral polysynth, the rear panel is nice’n’simple. It starts with quarter‑inch unbalanced stereo outputs and an associated headphone output. (It would be nice if the latter were on the front somewhere, but it isn’t, so let’s move on.) Next come pedal controller inputs for sustain, volume, the filter cutoff frequency and a multi‑function input that allows you to start or gate the sequencer and arpeggiator, as well as allowing you to use an audio signal to trigger the contour generators or step the sequencer or arpeggiator. MIDI is handled by a full complement of 5‑pin DIN sockets — in, out and thru — as well as USB, which carries MIDI but not audio. The Trigon‑6 is class compliant so no drivers are needed on either the Mac or PC. Happily, the front panel transmits parameter changes as MIDI CCs and NRPNs, which means that you can control other equipment and automate the synth itself. The final hole is an IEC mains input for its internal, universal power supply.

The Trigon‑6 Desktop Module

Sequential Trigon-6

While I was writing this review, there was much speculation about whether Sequential would release a Trigon‑6 module. Some of this was fuelled by the description of poly‑chaining in the manual, which, even before the recent announcement, stated that, “If you have two Trigon‑6 synthesizers you can link them together with MIDI to increase the total available polyphony to 12 voices... If you have a Trigon‑6 keyboard and a Trigon‑6 module, you will most likely use the keyboard as the master and the module as the slave.” Given the existence of the Prophet 6 and OB‑6 desktop modules, I was pretty certain that a Trigon‑6 module was in development.

Shortly after I submitted this review (the first time) all was revealed. So I asked myself, why might you be interested in the desktop module? Other than the obvious considerations of space and convenience, I can think of two significant reasons. Firstly, the 49‑note keybed of the Trigon‑6 may make the combination of the desktop module and a wider MIDI controller your preferred version. Secondly, the module recognises MPE. As I write, there’s no information regarding the messages recognised and the destinations to which you can direct them, but I think that we can be confident that independent, per‑note modulation of pitch, filter cutoff frequency and loudness will be possible.


  • It sounds great.
  • It looks great.
  • It’s simple to use.
  • It’s solidly built.


  • The keyboard will be unsuitable for some players.
  • There are a couple of unexpected voicing limitations.
  • It would benefit from a modern screen.


Dave Smith’s last synthesizer may not turn heads like a dual‑manual Prophet 10 or even the recent Prophet 5/10 Rev 4, but it’s an attractive and fine‑sounding polysynth. And, when it comes down to it, that’s what Dave did throughout his career — he gave us great instruments that we enjoyed using and our audiences loved hearing.


£2999, desktop version £2399. Prices include VAT.

$3499, desktop version $2499.