Sequential introduces Fourm, a compact analog synthesizer with polyphonic aftertouch
Sequential has unveiled the Fourm, a compact four-voice analog synthesizer that marks the company's return to polyphonic aftertouch technology after a 40-year hiatus. The instrument combines classic Prophet-5 voice architecture with modern performance capabilities in a portable format.
At the heart of Fourm lies an analog synthesis engine built around oscillator and filter chips inspired by vintage Sequential designs. The dual-oscillator voice architecture draws from the Prophet-5 Rev 2, utilizing a modern implementation of the classic oscillator design that maintains the original's characteristic tone while improving stability and consistency. The 4-pole low-pass filter includes bass compensation, allowing musicians to increase resonance without sacrificing low-end frequencies.
The standout feature is Sequential's newly developed Tactive keybed, a custom 37-note slim-key design with polyphonic aftertouch. This technology enables per-note expression control, allowing players to modulate individual notes independently through finger pressure. The implementation represents Sequential's first use of polyphonic aftertouch since the 1980s, opening new possibilities for articulation and dynamic control.
Fourm's modulation section takes inspiration from the Sequential Circuits Pro-One, featuring a hands-on matrix system with clearly labeled sources and destinations. The top-panel interface allows for immediate sound shaping through button-press connections and color-coded indicators. Musicians can route polyphonic aftertouch to multiple synthesis parameters directly from the panel.
Additional features include a polyphonic step sequencer supporting chords, ties, rests, and per-step glide, plus a six-mode arpeggiator with re-latching and repeat settings. The instrument offers unison mode for stacking all four voices, dual ADSR envelopes modeled after Prophet-5 response curves, and simultaneous wave selection for complex timbres.
The synthesizer houses its components in a solid steel chassis and includes standard connectivity options: MIDI in/out/thru, USB-C, quarter-inch audio output, headphone jack, and connections for sustain and expression pedals. A high-contrast OLED screen provides preset browsing and access to deeper synthesis parameters.
Sequential designed Fourm to bridge vintage analog sound with contemporary performance demands, creating what the company describes as a "no-compromise, all-analog instrument" for modern synthesists. The instrument is now available through Sequential's authorized dealer network including Perfect Circuit.