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GS Music e7

Polyphonic Synthesizer By William Stokes
Published July 2023

GS Music e7

Newcomers GS Music are kicking things off in style with an ambitious polysynth.

Considering the GS Music e7 is purportedly the first ever analogue polysynth to be designed and manufactured in its developer’s native Argentina, I’ll assume it’s no coincidence that not six months after the nation’s momentous World Cup victory, a unit arrives at my studio sporting a striking white and light blue finish. This said, I should mention that the e7 is in fact also available in three other colour schemes: blue and grey, blue and black, and red and black, and all with rather nice wooden side panels to boot. It started life back in 2019 as a prototype called the Zeus, a 12‑voice polyphonic keyboarded instrument not visually dissimilar to the Moog Voyager, before evolving into the seven‑voice desktop synthesizer that sits before me today.

Out Of The Box

Suffice to say, unboxing a large‑format desktop synth of the e7’s ilk is always a nice experience. It’s weighty, well‑built and, well, it’s big; 52cm by 19cm to be exact. I daresay that in today’s world of sleek, scaled‑down analogue instruments by boutique companies (just look at Superlative’s Monolab System 1000, announced at this year’s Superbooth), it’s something of a statement of intent to make a palpably classic‑looking desktop synthesizer; one more akin to the likes of Oberheim’s desktop iteration of the OB‑X8. The e7 presents a spacious panel, replete with Moog‑style knurled knobs offering near one‑to‑one functionality (save the inclusion of a Shift key and a few simple menus). Its classic feel extends, for better or for worse, to the slightly light, even plasticky feel of the aforementioned knobs, vaguely recalling vintage synths like the original Sequential Pro One. In fact, the e7 would look like it could be from any decade if it weren’t for its little OLED screen.

I mean it when I say ‘for better or for worse’: while the build quality of the e7 errs on the raw side, it’s worth saying straight off the bat that GS Music have done very well to keep the e7’s price as low as it is. Don’t forget that we still live in a world where many components are in short supply; I’d imagine a few creative workarounds were required to get the full bill of e7 parts to Buenos Aires and keep the whole operation solvent. I suspect its desktop form factor also helped in this respect, with GS Music ditching the Zeus’s keyboard and prioritising connectivity over controllers (there’s no onboard sequencer either). This it has glorious amounts of, with USB, 5‑pin MIDI, CV and even MPE control all happily accepted by the e7.

The e7’s rawness, I should say, is palpable: some of the physical knobs don’t quite align exactly with their actual digital values, for example, and there’s a faint but noticeable noise floor that makes me think of the Korg MS‑20. This might have been an irritation if it wasn’t for the e7’s character and playability, which, like the MS‑20, it has in spades. Its digital brain and rudimentary effects section make the most of an otherwise all‑analogue signal path, boasting a variety of control modes and an impressive 600 preset slots. This said, the e7’s architecture — at least on first glance — is based around a fairly conservative design. Or, should I say, an elementary one, in the sense that it also does well to present a great introduction for anyone into the craft of subtractive synthesis, helped along by its well‑written and intentionally educational manual.

The rear panel offer full size MIDI in, out and thru, quarter‑inch CV inputs for pitch, cutoff and gain, an external audio input and stereo and headphone outputs.The rear panel offer full size MIDI in, out and thru, quarter‑inch CV inputs for pitch, cutoff and gain, an external audio input and stereo and headphone outputs.


The e7’s two identical oscillators offer triangle, saw and triangle‑saw waves, alongside a layerable pulse‑width‑variable square wave and additional square‑wave sub‑oscillator. They can be hard sync’ed, and there’s also a handy autotune function, which snaps things into tune in an impressive two seconds or less. There’s a noise generator which doubles as a volume control for external audio when connected, and adjustable portamento. So far so good. They’re punchy, raw and feel ever‑so‑slightly drivable; not dissimilar to the incredible‑sounding oscillators on the Analogue Solutions Leipzig, which I reviewed back in 2021 and still love to this day. In fact, it’s worth pointing out that with no stabilising CPU on board the Leipzig, it was prone to some oscillator drift, which the e7, happily, is not. The e7’s 24dB/octave filter is decent and smooth across its 10Hz‑25kHz range, though its resonance never quite self‑oscillates into true ‘howl’ territory, which felt somehow out of character with the rest of the e7’s design. It has scope for plenty of movement beyond conventional enveloping, though, and can be modulated by any or all three LFOs simultaneously, as well as be influenced by the mod wheel, note velocity, aftertouch and keyboard tracking.

As you might expect, two ADSR envelopes control the movement of the filter and VCA respectively. In addition to this there are two rather lovely elements of expression on both envelopes, accessed via the Shift key: the first is a velocity modulation parameter on both the attack and release stages, which shortens both the harder a key is played. The second links keyboard tracking to the decay stage, shortening the decay time as you move up the keyboard. This, say GS Music, simulates the perceived shortening of high note decay times on acoustic instruments like pianos and guitars, and it does so effectively. There’s also keyboard tracking on the overall VCA level, which when dialled in tastefully also helps achieve this natural feel. I have to say that, despite all of this, I would still like to have seen a sustain pedal input, but as it is there’s a fine array of keyboard‑based expression on offer for keyboardists of that persuasion.

Other colours are available...Other colours are and and and and black......or blue and black....or blue and black.The e7’s screen is a well‑proportioned inclusion, helpfully showing graphical readouts of EQ filtering and resonance, envelope curves, oscillator frequencies and more. While the screen displays a moving readout of the chosen VCO waveform, don’t be fooled into thinking this is an oscilloscope, as found on the likes of Korg’s Monologue. It accurately tracks the pulse width of the square wave, yet does little else beyond showing what’s already displayed on the physical panel next to the oscillator section. An oscilloscope isn’t essential, of course, but it can certainly help with sound sculpting — particularly when tweaking, hard sync’ing, modulating and melding seven voices of analogue goodness. Perhaps that’s for a future firmware update.

Enter The Modulation Matrix

Three LFOs furnish the e7’s modulation matrix, each with slightly different functions. They can all generate triangle, saw, reverse saw and square waveforms, while LFOs 1 and 2 also offer random voltage generation. This I’m always happy to see included; more so two of them, and particularly in a polyphonic instrument geared toward functioning in a live setting, since randomness tends to be the very thing that can help make electronic instruments feel, well, live! There’s a decent amount of flexibility here while still maintaining a relatively WYSIWYG interface: LFO 2’s frequency can itself be modulated by one of the envelope generators, while LFO 3 is automatically set to be attenuated by mod wheel CCs, and can also be set to respond to aftertouch. Each can just about touch audio‑rate frequencies, so while FM‑style sounds don’t come naturally here, they’re not off the table.

The multi‑mode nature of LFOs 1 and 2 is a real asset to the e7’s sound: they can be set to oscillate in phase across all of its voices for huge, singularly undulating modulation; they can subtly move in and out of phase with each other across different voices for polyphonic depth; or they can retrigger a completely new wave for each voice, resulting in rippling, complex movements across chords and melodies. There’s also a keyboard tracking mode that increases the LFO frequency with the note value, and clock sync’ing, with the option to have the phase difference between sequentially triggered LFOs quantise to clock divisions, which is smart. As someone who appreciates a visual cue where possible, I’d have appreciated an LED for each LFO to represent their respective movements in real time, particularly as the VCA envelope’s behaviour is quite capably represented by the LEDS in the e7’s Voices section, but as it is the LFOs don’t leave much to desire. I daresay this would also have complicated things when it comes to triggering multiple LFOs in Polyphonic or Multitimbral mode, discussed anon. Over on the other side of the panel, in the VCA section, is a parameter for stereo spread, which when adjusted handily prompts the e7’s screen to display where each voice is place in the stereo field. This can also be modulated for some simple and rather lovely Oberheim‑esque stereo movement. Great stuff.

The e7’s effects section is decent, presenting a chorus and digital delay. Similar to the e7’s filter, the delay feels fairly safe, never reaching self‑oscillation or any pitch‑shifting chaos when shifting the delay time. As a means of bolstering the depth of the e7’s output, though, it’s very useful and does its job very well, as does the chorus. Both offer different modes; the delay can be clock sync’ed, usefully, and be set to unify across the stereo field or to ping‑pong. The chorus has a Basic mode and an Ensemble mode, which sounds to me like it shoots an additional LFO through the phasing of the delayed chorus signals. The e7 manual proudly says Ensemble mode “adds a different dimension to the sound, simulating a string or vocal ensemble”, and I’d say that’s about accurate, if a slightly floral description.

Mono Power, Multi Madness

When it comes to its monophonic side, the e7 delivers equally well with copious amounts of variety on offer. Beyond the conventional Polyphonic mode, which retriggers both envelopes with each of the e7’s seven voices, there’s a monophonic Single Trigger mode (triggering the envelopes just once at the top of each held phrase) and a Multi Trigger mode (retriggering the envelopes with each note). There’s also a single and multi‑trigger Unison mode, lushly making use of all seven voices at once for some potentially huge sounds. While I could nitpick and say I’d like to have seen a single‑trigger polyphonic mode thrown in there as well, I can’t complain at this level of choice. Apart from anything else, I can safely say that if the e7 were exclusively a monosynth I would consider it a very powerful one, and that’s before we even arrive at its four‑part Multimbral mode.

Multitimbral mode opens up considerable sound‑design opportunities in the e7 — both tonal and atonal — with the addition of moveable keyboard zones, which expands the scope of the instrument considerably. I enjoyed flicking through some of the e7’s multitimbral factory presets, particularly one that used a combination of modulated noise and tonal oscillators to achieve a pulsing electronic cymbal and bass combination. When it comes to creating your own voices, it’s a case of using the Preset buttons at the bottom of the panel to move between the four parts (or timbres), then sculpting a different sound for each: the oscillator, filtering, modulation, enveloping and more can all be individually set for each part to achieve anything from subtle, finely‑tuned variance to wild and complex sounds packed with texture and different layers of movement. As with many other aspects of the e7, there’s a healthy amount of limitation here: four‑part multitimbrality might not sound as impressive as some other synths out there, but in the real world it’s plenty for creating brilliant sounds. There’s even a nifty on‑screen graphic mixer to help strike just the right level balance between parts.

I should say that Multitimbral mode doesn’t present the most intuitive way of navigating between different parts and editing them, with its combination of buttons and the screen menu, and on more than one occasion I found myself accidentally stumbling into a factory preset with no immediate way of returning quickly to what I was working on. But, as is often the case, things got easier with repetition. The only global values Multitimbral mode is subject to are the e7’s effects and stereo spread settings, which if nothing else ends up a great way to keep everything cohesive, even at subtle settings. I almost found myself wishing for a one‑knob compressor to cap it all off.

Having sculpted my four‑part multitimbral ensemble I can say that while it was certainly enjoyable to have the sound lurch as one weighty block between notes on the keyboard or sequencer (indeed, sequencing this kind of thing at speed is always a thrill ride), the e7’s moveable keyboard zones do a fantastic job of endowing it with true, musical applicability. They were also a breeze to program, courtesy of a screen‑based readout of the chromatic keyboard and a visual representations of where zones begin, end and overlap. Strengthen the left‑hand parts with some sub bass, add airy noise to the upper reaches of the keyboard, or have the two halves of the keyboard completely distinct from one another as if playing two different synths. It’s also possible to have sounds blend and overlap with each other in one long continuum across the keyboard, adding all manner of exciting dynamism and texture to sequences and melodies as they move across the e7’s range. It’s even possible to have ‘dead zones’ in the keyboard, which could come in very handy if, for example, you’re sending your controller to one or more other destinations alongside the e7 and want to keep them distinct from each other.

The e7 is seizing its moment to muscle in among the polyphonic analogue heavy hitters, more than happy to announce itself as a classic‑in‑waiting...


As I say, the e7 occasionally feels rough and ready, but its focus is demonstratively on the things that matter: sound and character. It’s got depth and real substance, but it’s also got attitude and edge. All things considered, it seems the e7 is seizing its moment to muscle in among the polyphonic analogue heavy hitters, more than happy to announce itself as a classic‑in‑waiting while punching above its price point quite considerably. Only time will tell if that wait will pay off in the public sphere, but it has all the makings of a mainstay on the synthscape and throws down the gauntlet to synths double its price. As an Englishman, I can only hope that when football finally does come home, we’ll see a few home‑grown synths hitting the market resplendent in red and white. If they’re anything like this one, there’ll be more than one reason to celebrate.  


  • Great‑sounding oscillators with multiple avenues of expression.
  • Excellent Multitimbral mode with lots of editability.
  • Highly connective across USB, 5‑pin MIDI, CV and MPE.
  • Great value for money.


  • Slightly rough build quality.
  • Could show slightly more aggression in some areas!


An impressive, characterful and reliable analogue synth with onboard effects and oodles of flexibility.


£1799 including VAT.

KMR Audio +44 (0)20 8445 2446.