Sequential Fourm 4-Voice Analog Synth The Sequential Fourm is a compact, four-voice analog synthesizer designed to offer unprecedented expressive performance by combining legendary Sequential tone with highly responsive modulation capabilities. It is positioned within Sequential's "Modern Analog" lineup, embodying a philosophy of delivering classic sound architecture enhanced by contemporary engineering and expressive features. It delivers four genuine voices of 100% analog sound, right down to the characteristic envelope response curves of its legendary predecessor. Oscillators: The synth features two Prophet-5 lineage analog oscillators per voice. These oscillators utilize a modern chip inspired by the original Prophet-5 Rev 2 design, providing the same rich, musical tone but with improved stability, reliability, and consistency. All oscillators offer simultaneously selectable waveforms. Features include classic Prophet-style Sync and Variable square wave pulse width (PWM) per oscillator. Oscillator B can also function in low-frequency modes for use as a polyphonic LFO modulation source. Filter: The Fourm utilizes a 4-pole resonant lowpass filter chip based on a classic design known for its rich, organic tone and musical resonance. The filter is enhanced with bass compensation, a modern feature that allows users to crank the resonance without sacrificing low-end power, keeping the sound full and bold. The filter can be driven into self-oscillation and supports quarter, half, or full keyboard tracking. Envelopes and Feedback: The synth includes two four-stage (ADSR) envelope generators (one for the filter and one for the amplifier) modeled after the Prophet-5 s response curves. A dedicated Feedback path with an aggressive drive circuit provides extra edge to the tone, and three types of noise (white, pink, and violet) can be blended in at the mixer stage. Expressive Performance and Control A hallmark of the Fourm is its emphasis on player expression, driven by a custom-engineered keybed and comprehensive modulation options. Tactiveâ„¢ Keybed with Polyphonic Aftertouch: The Fourm features a custom-designed Tactiveâ„¢ 37-note slim-key keybed tuned to complement its analog synthesis engine. Crucially, Sequential has returned to polyphonic aftertouch for the first time in 40 years, an incredibly expressive performance feature. Polyphonic aftertouch provides a direct and nuanced connection between playing and per note synthesis parameters, allowing for independent articulation of notes played simultaneously. Up to six polyphonic aftertouch destinations are selectable simultaneously, including oscillator frequency, filter cutoff, and amplitude. Modulation: The modulation section takes inspiration from the classic Sequential Circuits Pro-One monosynth. It offers a hands-on modulation matrix with two modulation buses, multiple sources (filter envelope, Oscillator B, LFO) and destinations (oscillator frequencies, pulse widths, filter cutoff, amplitude, LFO parameters). The single global LFO offers seven waveshapes and can be synchronized to tempo. Unison and Glide: The synth includes a Unison (monophonic) mode configurable from one to all four voices, complete with chord memory. A Vintage setting adds slight voice-to-voice variations in component behavior to recreate classic analog synth characteristics. Polyphonic glide (portamento) is also available to control note transitions. Sequencing and Connectivity For composition and performance, the Fourm includes powerful sequencing tools and flexible I/O. Arpeggiator and Sequencer: Fourm features an arpeggiator with six classic modes, which responds musically to playing. Tucked into this section is a polyphonic step sequencer with up to 64 steps. This sequencer is a creative powerhouse, supporting chords, ties, rests, and Acid-style per-step glide. It can also be used as a modulation source to trigger rhythmic filter patterns and other timbral effects. Design and I/O: The synth is housed in a pro-quality, all-steel chassis with an intuitive, knob-per-function layout. Connectivity includes standard MIDI in, out, and thru ports, USB-C for bidirectional MIDI, a footswitch/expression pedal input, a single unbalanced 1/4" mono main output, and a headphone output. Why We Love It Our Gear Experts appreciate the Sequential Fourm for its unprecedented expressive performance using polyphonic aftertouch on the Tactiveâ„¢ keybed. It delivers the legendary 4-voice analog tone of the Prophet-5, enhanced with a classic 4-pole filter featuring bass compensation. The hands-on, Pro-One-inspired modulation matrix and powerful polyphonic step sequencer make it an intuitive creative powerhouse. Features: ¢ 4-Voice Analog Synth: Provides four genuine voices of 100% analog sound. ¢ Prophet-5 Voice Architecture: Built on the legendary architecture of the Prophet-5, including its characteristic envelope response curves. ¢ Dual Analog Oscillators: Two Prophet-5 lineage analog oscillators per voice. ¢ Simultaneously Selectable Waveforms: All oscillators have simultaneously selectable waveforms. ¢ Tactiveâ„¢ Keybed: Custom-engineered 37-note slim-keys keybed. ¢ Polyphonic Aftertouch: An incredibly expressive performance feature that brings per-note articulations to your fingertips. ¢ Classic 4-Pole Low-Pass Filter: Based on a legendary design known for its rich, organic tone and musical resonance. ¢ Filter Bass Compensation: Allows you to crank the resonance without sacrificing low-end power. ¢ Pro-One Style Modulation Matrix: Hands-on modulation section inspired by the Sequential Circuits Pro-One. ¢ Polyphonic Step Sequencer: A creative powerhouse with up to 64 steps, supporting chords, ties, rests, and Acid-style per-step glide. ¢ Sequencer as Modulation Source: The step sequencer can be used to trigger rhythmic filter patterns and other timbral effects. ¢ Unison Mode: Monophonic mode with configurable voice count (one to all four voices) and chord memory. ¢ Vintage Setting: Recreates classic synth characteristics by adding voice-to-voice variations in component behavior. ¢ Aggressive Drive Circuit: Included in the Feedback path for extra edge and fullness. ¢ USB-C MIDI Connectivity: Allows for bidirectional MIDI communication.