Analog Synth

Sequential Fourm

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Sequential Fourm review

Legendary sound, excellent value Determined to occupy the entry-level of the market, Sequential presents the smallest polyphonic analog synth in its history, the Fourm, offering a typical Prophet-5 sound and a slim polyphonic pressure keyboard. Read more…

Tech. sheet

Created on 09/23/2025

Manufacturer: Sequential
Model: Fourm
Category: Analog Synths
Release date:september 2025

Polyphony: 4 voices, monotimbral; unison modes (1 to 4 voices), fine detune, chord memory; vintage parameter for voice variations.
Keyboard: 37 slim keys, velocity, polyphonic aftertouch (poly pressure), 2 transposition keys (±2 oct.).
Oscillators: 2 VCOs (SSI2131) with cumulative waves (A: sawtooth + variable pulse; B: triangle + sawtooth + variable pulse), 4 oct. tuning, B→A sync, noise generator (white/pink/violet), temperaments (65).
Filter: 4-pole low-pass (SSI2140) with compensated resonance, self-oscillation, adjustable feedback circuit.
Envelopes: 2 ADSR (VCF/VCA), inspired Prophet-5 response, routable velocity on envelope amount.
LFO: global, multiple wave cumulants (sawtooth/ramp/triangle/square/S&H/random/noise/DC), clock sync, going all the way to audio.
Modulation matrix: Env-VCF/Osc B/LFO sources to 8 destinations (freq A, freq B, PWM A, PWM B, cutoff, amplitude, freq LFO, amount LFO) + wheel; poly aftertouch with 3 buses/2 destinations each.
Arpeggiator/Sequencer: arp modes up/down/pendular/alternated/random/order; note repeats 0-3; poly 4 voice sequence up to 64 steps; step-by-step recording (notes, silence, link, glide) or parameter automation; keyboard transposition; MIDI send.
Memory: 4 banks × 128 programs (2 factory + 2 user); selection by bank/number or 16 categories.
Controls & interface: OLED display, numerous direct controls, Param key, screen-printed secondary functions, Select push-button encoder; Basic Program function; no front-panel display of values during editing.
Connections: mono audio output, headphones, assignable pedal (switch/continuous) in 6.35 mm, trio MIDI DIN, USB-C (MIDI, CC/NRPN, programs, update), external power supply 12 VDC/1.2 A.
Construction/format : screwed metal shell; 56×25×7 cm (22 x 9.8 x 2.8 inches) ; 4 kg. (8.8 lbs.)

Videos

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Q&A

Does the Fourm offer a polyphonic aftertouch that can be used for different modulations per note?

Yes. The slim keyboard supports polyphonic aftertouch with three buses and two destinations per bus, assignable independently on each voice.

What type of filter is it, and can resonance compensation be disabled?

It's a resonance-compensated 4-pole low-pass (SSI2140); compensation cannot be disabled.

How much program memory is available in total?

512 locations: 256 factory presets and 256 user programs (4 banks × 128).

Is the LFO polyphonic?

No, it's global (monodic), but it has many shapes that can be accumulated, synced to the clock, and goes right up into the audio. Constant low-frequency oscillator B can be used in the modulation matrix to create a polyphonic LFO.