Why Sequential’s Fourm has a whole new mode of expression“It’s not a toy; it’s a serious, pro-level instrument, just in a smaller form factor. No pun intended.” That’s Sequential product designer Carson Day assuring me that the brand’s latest synthesizer, Fourm, is ready for the big time.
A compact four-voice poly analogue synth that weighs just 4kg and costs £800 ($999), Fourm is diminutive compared to any other instrument that Sequential currently stocks — you can see why some synth-lovers might worry that the brand founded by the late legend Dave Smith has strayed into cheap and cheerful territory. Thankfully, this is not the case. Fourm is a powerful and expressive instrument with a clear goal in mind: to offer a more accessible way into Sequential’s iconic lineup of synthesizers.

READ MORE: Sequential Fourm is like a Prophet, minus one voice and several thousand dollars

Fourm boasts a voice descended from the famed Prophet-5 synthesizer. First released in 1978, the Prophet series were the first programmable synthesizers on the market. The pioneering vision of Dave Smith led to his sound appearing on the records of music royalty going back decades. Kraftwerk, Madonna, Michael Jackson, Phil Collins, Radiohead — the ‘Sequential Sound’ has its sonic fingerprints all over the last four and a half decades of music history.
From head to toe, Fourm’s circuitry is fully analogue with callbacks to previous models that core Sequential fans will be happy to hear. As Carson explains, “The foundation for all of our instruments is having a great-sounding base signal path. In this case, it’s 100% analogue. We have VCOs using some SSI chips that are really fantastic. Those go through the analogue filter that we use in the Prophet Rev 4 […] and then into analogue VCAs. We wanted to make something that sounds great and has that classic Sequential Prophet sound.”
Sequential synths have mainly been the domain of dedicated synthesisists willing to pay high premiums. Previously, the Take-5 held the spot for the most affordable synthesizer, and even then, it costs £400-500 more than the Fourm. Being able to access the Sequential sound at a significantly lower price is certainly attractive. Dave Gibbons, CEO of Sequential, makes clear that the company wants to welcome synthesis newcomers. “The primary target was [making] something for people who are not the usual buyer of our stuff and who are looking to get into it for the first time, maybe a bit intimidated by the complexity and the price point of the higher instruments.”
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While Fourm boasts a high-quality analogue sound engine and premium build quality, it also keeps its user interface deliberately simple. Most features have been given a physical home on a button or knob, with very little hidden inside the display menu. Its features include two analogue voltage-controlled oscillators, a classic 4-pole resonant lowpass filter with bass compensation, two ADSR envelopes, a Pro-One style top-panel modulation matrix, aftertouch controls, a low-frequency oscillator and an arpeggiator.
The one-function per dial design means the Fourm keeps all the core synthesis tools at easy reach, ideal for quick switching between performance and sound crafting. It’s a design ethos clearly intended to reach average musicians and keyboardists.
“We wanted to make something that’s accessible to non-synthesists,” Carson says. “Let’s say a bassist, or a guitarist, or a drummer, or a lead singer. They can have something that has great sounds, is portable, easily put on stage, but then also has an interface that, if you want to start exploring synthesizers and synthesis, you can just grab knobs and see what happens and start your learning.”
Many of Sequential synths are large instruments with full-size keys, but the Fourm sports smaller-sized ‘slim-keys’ — another reason some might dismiss it as toy-like. But Gibbons assures that, while they are shorter in width, they are still quite long, allowing room for the hand to manoeuvre and stretch out. Smaller keys also means that the Fourm covers 3 full octaves. A dedicated synth player might not have any trouble flipping between octaves using buttons, but a keyboard player, on the other hand, will appreciate having access to a wider range of playable notes in front of them.
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Perhaps the biggest drawback is the noticeable lack of onboard effects processing, which cuts into its utility as an all-in-one touring instrument. But Sequential tries to make up for this by providing a rare feature that hasn’t been seen in a Sequential instrument for a long time: a custom-designed polyphonic aftertouch keybed. This is the first time that Sequential has worked with the technology in 40 years.
If you’re not familiar with polyphonic aftertouch, the premise is simpler than it sounds: sensors are installed underneath the keys to record the individual pressure of each note (up to four in this case). So, while you hold down a note or chord, you can simultaneously press and ease the keys to change the sound. Without lifting your hands, you can control settings such as the frequency, filter, LFO and more.
Rubbing, kneading, massaging — however you want to describe the action, it’s an unusual technique to try out, and one that lots of synth players seek out. Sequential’s 20-person team worked on developing the keyboard — now trademarked as Tactive — in a way that was tightly integrated with Fourm’s sound engine. Over regular meetups that brought together mechanical engineers, software engineers, electrical engineers, designers and players, the team laboured over getting the polyphonic aftertouch feature working just right. Refining in this way and choosing not to use off-the-shelf technology is what Gibbons describes as the “magic sauce”, adding that their success was due to “the ability to have control of all those variables, and to have the people who are designing around them react all at the same time.”
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Bending notes individually or opening filters with the press of a finger are a couple of ways the Fourm creates a brand new way of playing. In Gibbons’ opinion, aftertouch could even be used to shortcut what normally requires added setup to achieve: “It didn’t take too long after we started playing with it, before you realise ‘I’m kind of doing something with the aftertouch now that I would have set up a split to do on a bi-timbral keyboard before.’”
As a whole, the Fourm fills a long-time gap in Sequential’s catalogue. Its small form-factor, coupled with the classic Prophet sound, will be a drawcard for fans who have never had the ability to invest in a Sequential synth in the past. To bridge the gap left by the lack of onboard effects processing, the polyphonic aftertouch offers an interesting alternative to layering expression and sculpting sounds. With all these features elegantly packed into a small frame, the Fourm is an unusual but powerful analogue synth.
As Carson reflects, the team at Sequential set themselves a clear goal: “Let’s get something that sounds like our instruments and that delivers in a weight, an impact, and a beauty that has been reflected in our instruments for years.”
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