Sequential Fourm Polyphonic Analogue Synthesizer

Fourm is an innovative compact analogue synthesizer designed to inspire creative freedom and performance expression. Featuring the next evolution of Sequential’s legendary tone, a tactile knob-per-function interface and the groundbreaking Tactive™ polyphonic aftertouch keybed, Fourm is a powerful instrument built for modern synthesists who demand immediacy, nuance and unmistakably analogue presence.

From classic Prophet-style warmth to dynamic hands-on modulation, Fourm delivers a performance experience that is deeply musical, intuitive and expressive.

Main Features

• Tactive 37-note slim-key keyboard with polyphonic aftertouch
• 100 percent analogue signal path
• Knob-per-function layout for immediate control
• Pro-One-inspired top-panel modulation matrix
• Prophet-lineage 4-pole resonant filter with bass compensation
• Arpeggiator with sequencer integration
• 256 professionally designed presets
• Premium all-steel chassis

Pure Sequential Analogue Design

Fourm’s four true analogue voices are based on the revered Prophet-5 architecture, complete with its signature envelope curves and unmistakable warmth. With dual oscillators offering simultaneous waveform selection, plus a 4-pole low-pass filter featuring bass compensation, Fourm captures the timeless Sequential character and extends it for a new generation.

Dual Analogue Oscillators

Modern oscillator design inspired by the original Prophet-5 Rev 2 provides:

• Vintage richness
• Modern reliability and tuning stability
• Enhanced consistency for live and studio use

4-Pole Filter with Low-End Integrity

Boost resonance without losing power. The filter retains weight and definition even at high settings—perfect for sculpting bold basses or shimmering leads.

A New Dimension of Expression

Tactive™ Keybed

Custom-designed slim keys deliver a responsive, balanced feel suited to fast articulation or expressive sustained playing.

Polyphonic Aftertouch

Control per-note modulation, filter sweeps, vibrato, pitch gestures and evolving timbres directly from the keybed. Fourm brings back a performance feature not seen on a Sequential keyboard for over 40 years.

The result: a deeper, more emotional connection between player and instrument.

Hands-On Modulation Inspired by Sequential History

The modulation section draws from the revered Sequential Pro-One, a cult classic famous for its punchy basslines and hands-on routing. Fourm takes this proven design and expands its interaction possibilities, letting you experiment with:

• OSC modulation
• Filter movement
• Rhythmic shaping
• LFO texture
• Env-based movement

Turn ideas into sound instantly—no menus required.

Arpeggiator and Sequencer: Performance Engines

Flexible Arpeggiator

Six responsive modes allow everything from hypnotic rhythmic cycles to evolving harmonic patterns, with options including:

• Multi-octave spread
• Re-latching behaviours
• Syncopated repeat timing (e.g. dotted 8ths)

Deep Polyphonic Sequencer

Go beyond playback. Shape modulation movement, build patterns and create evolving textures.

Supports:

• Chords
• Ties
• Rests
• Per-step glide (Acid style)
• Filter and parameter sequencing
• Modulation integration

Fourm is as powerful for composition as it is for performance.

Specifications

Synthesis

• Dual analogue oscillators with simultaneous waveform selection
• Prophet-style oscillator sync
• Classic 4-pole resonant low-pass filter
• Bass compensation
• Feedback with dedicated drive circuit
• 2 x ADSR envelopes
• LFO with full waveform selection

Sequencing

• Polyphonic step sequencer
• Glide per step
• Modulation capable

I/O

• Mono main output (¼ inch jack)
• Mono headphone out (¼ inch TRS)
• MIDI In/Out/Thru
• USB for bidirectional MIDI
• Footswitch/expression input

Power

• Separate power switch
• 12V DC 1.2A supply included
• Global AC compatibility (100–240 V, 50/60 Hz)
• 14W maximum consumption

Dimensions

• 22.13 x 9.88 x 2.75 inches (56.2 x 25.1 x 7.0 cm)
• Weight: 8.76 lbs (3.97 kg)
• Anti-theft slot

Fourm is not just another compact synthesizer—it is an expressive, beautifully engineered analogue instrument shaped by Sequential’s heritage and crafted for players who value tactile depth, tonal authenticity and direct musical connection.