Description
The Sequential Fourm is a compact 4-voice analog synthesizer built on the legendary Prophet-5 architecture, delivering warm, punchy tones through dual oscillators and a 4-pole resonant low-pass filter with bass compensation. Its 37-note Tactive™ slim-key keyboard with polyphonic aftertouch offers expressive per-note control for subtle dynamics and dramatic gestures. The Pro-One-inspired modulation matrix allows quick routing of sources to destinations with visual feedback for complex sound design. Fourm features oscillator sync, PWM, dual ADSR envelopes, multiple LFO shapes, and feedback for versatile analog tone shaping. Performers benefit from a polyphonic step sequencer, arpeggiator, unison, portamento, and vintage voice variation for creative expression. Housed in a professional all-steel chassis with USB-C, MIDI, pedal inputs, and 12V DC power, Fourm blends classic analog warmth with modern hands-on control for studio or stage.


Analog Oscillators & Filter
Fourm delivers two Prophet-5 lineage oscillators per voice with simultaneous waveform selection and classic sync, passing through a 4-pole resonant low-pass filter with bass compensation for thick, punchy analog tones.


Polyphonic Aftertouch
The 37-note Tactive™ slim-key keyboard offers polyphonic aftertouch, allowing expressive per-note modulation including oscillator pitch, filter cutoff, amplitude, and LFO parameters for nuanced performances.


Hands-On Modulation
Inspired by the Pro-One, the top-panel modulation matrix provides immediate access to sources and destinations, enabling complex modulation paths with color-coded visual feedback and flexible routing in seconds.


Sequencer & Arpeggiator
Fourm includes a polyphonic step sequencer with 64 steps and acid-style glide per step, alongside a versatile arpeggiator with six modes, re-latching, and tempo sync, supporting creative composition and performance workflows.
Two Prophet-5 lineage analog oscillators per voice with simultaneous waveform selection and classic sync
4-pole resonant low-pass filter with bass compensation and self-oscillation capability
Tactive™ 37-note slim-key keyboard with polyphonic aftertouch for expressive performance
Pro-One style top-panel modulation matrix with flexible source/destination routing
Polyphonic step sequencer with 64 steps and per-step glide plus arpeggiator with six modes
Unison (monophonic) mode and polyphonic glide (portamento) for versatile playability
Vintage mode adds voice-to-voice variations for authentic analog character
100% analog signal path with feedback, noise types, and dual ADSR envelopes for tone shaping
Intuitive knob-per-function layout with spring-loaded pitch wheel
Robust, all-steel chassis for stage and studio use
Synth Type: Keyboard Synth
Sound Generation: Analog
Keyboard: 37 Slim Keys with Synth Action
Touch Sensitivity: Yes
Aftertouch: Polyphonic Aftertouch (Destination Assignable)
Expression Controls:
1x Pitch Bend
1x Modulation
Display: Monochrome LCD
Number of Sounds, Kits, or Samples: 128x Factory Sound Preset
Maximum Polyphony: 4 Voice
Multitimbrality: 1-Part
Performance Functions: Arpeggiator, Octave Shift, Sequencer
Oscillators: 2x Variable (Sawtooth, Sine, Square)
Mixer: Oscillator, Oscillator 2, White Noise (Level)
Amplifiers: 1x VCA
Envelopes: 2x Filter/VCA/Assignable Envelope Generator: Delay, Attack, Decay, Sustain, Release
Filters:
Number of Filters: 1
Characteristic: Analog CEM 3320 Chip
Type: Low-Pass
Slope: 4-Pole/24 dB (LPF)
Controls: Cutoff, Resonance, Envelope Amount
LFOs:
Number of LFOs: 1x Global
Waveforms: Sawtooth Up, Sawtooth Down, Square, Triangle, Random, Sample & Hold
Controls/Modes: Clock Sync
Destinations: Oscillator 1 Frequency, Oscillator 2 Frequency, Oscillator 1 and 2 Pulse Width, Low-Pass Filter Cutoff, VCA, VCF, VCO, Filter Cutoff, Amp
Modulation Matrix: 11-Slot per Patch (3 Sources / 8 Destinations)
Aftertouch Destinations: Amplifier Envelope Amount, Filter Cutoff Frequency, LFO Amount, Low-Pass Filter Cutoff, Oscillator 1 Frequency, Oscillator 2 Frequency, VCA
Glide/Portamento: Yes
Arpeggiator: Yes
Audio I/O:
1x 1/4″ TRS Main Output
1x 1/4″ TRS Unbalanced Stereo Headphone Output
Pedal Support: 1x 1/4″ Expression/Footswitch
MIDI I/O:
1x DIN 5-Pin Input
1x DIN 5-Pin Output
1x DIN 5-Pin Thru
USB I/O: 1x USB-C (Host Connection, MIDI)
Power Requirements: AC/DC Power Adapter (Included)
AC Input Power: 100 to 240 VAC, 50 / 60 Hz
AC/DC Power Adapter: 12 VDC at 1.2 A, Center-Positive (Included)
Power Consumption: 14 W
Color: Black
Dimensions: 22.1 x 9.9 x 2.8″ / 56.1 x 25.1 x 7.1 cm
Weight: 8.8 lb / 4 kg













