Sequential Fourm – 4-Voice Analog Synth with Polyphonic Aftertouch

The Fourm is a compact, expressive analog synthesizer built for deep musical interaction. With Sequential’s signature tone engine, hands-on modulation, and a Tactive™ keybed featuring polyphonic aftertouch, Fourm empowers performers to sculpt each note in ways rarely possible on modern synths. Discover new levels of nuance with Soundium.

Key Features

• Tactive slim-key keyboard with polyphonic aftertouch: 37 keys designed to respond individually for per-note expression
• 100% analog voice architecture: Dual oscillators, Prophet-style 4-pole resonant filter, and full analog signal path
• Pro-One style modulation matrix: Intuitive routing with clear source/destination controls and color feedback
• Polyphonic step sequencer & arpeggiator: Up to 64 steps, tie/rest support, per-step glide, and modulation routing
• Unison + vintage mode: Stack voices or introduce intentional component variation for character and warmth
• Robust construction: All-steel chassis with intuitive, knob-per-function layout for immediate control

Customer Benefits

With Fourm, you get a hands-on synth that rewards performance. Polyphonic aftertouch adds a whole layer of expression—each note can evolve independently as you press deeper. The modulation matrix removes menu diving, encouraging spontaneous creativity. Whether layering pads, creating melodic textures, or morphing evolving soundscapes, Fourm bridges classic analog warmth with modern playability.

Quick Specs

• Voices: 4 analog voices
• Oscillators per voice: 2 analog with selectable waveforms; Osc B supports low frequency mode
• Filter: 4-pole resonant low-pass with bass compensation, self-oscillating capability
• Envelopes: 2 × ADSR (filter & amp)
• LFO: 1 global, 7 waveforms, syncable
• Modulation buses / matrix: 2 buses, multiple sources & destinations, combined routing
• Polyphonic aftertouch destinations (up to 6 simultaneously): Osc A freq, Osc B freq, filter cutoff, amplitude, LFO freq, LFO amount
• Arpeggiator: 6 modes, octave range, re-latching, repeat
• Step Sequencer: 64 steps, supports chords, ties, rests, per-step glide, modulation outputs
• Keyboard: Tactive™ 37-note slim-key with polyphonic aftertouch
• Chassis: Steel construction
• Dimensions (L × W × H): 56.2 cm × 25.1 cm × 7.0 cm
• Weight: 3.97 kg
• Outputs / I/O: Main mono out (¼"), headphone out, MIDI In/Out/Thru, USB-C MIDI, expression/footswitch input
• Power: 12 V DC, 1.2 A (100–240 V AC PSU included), ~14 W consumption

What’s in the Box

• Sequential Fourm synthesizer
• 12V DC power supply
• USB-C cable
• Owner’s manual
  

Use Cases / Ideal For

Fourm excels in studio and live performance settings where expressiveness matters. It’s perfect for those wanting rich analog voices with deep modulation and note-level nuance. Great for melodic lines, evolving pads, rhythmic sequences, and interactive performance setups.

Compatibility

Works with all major DAWs and hardware via USB-MIDI or traditional MIDI ports. Expression or sustain pedals can be used via the footswitch jack. Integrates seamlessly in hybrid rigs and modular setups.

Pros & Cons

✅ Pros:

• Polyphonic aftertouch in a fully analog four-voice synth—rare and expressive
• Modulation matrix and knob-per-function layout encourage hands-on design
• Powerful sequencing and arpeggiator tools built-in
• Premium build with steel chassis

⚠️ Cons:

• No onboard effects (reverb, delay) — external effects required
• 4 voices may be limiting for dense polyphonic patches

The Sequential Fourm offers a rare combination of pure analog sound, touch-expressive polyphonic aftertouch, and intuitive control—designed for musicians who demand immediacy and depth in every note.