• Subtractive analog synthesizer
• 37-key slimkey keyboard
• Polyphonic aftertouch
• 4 voices (incl. unison & mono)
• 2 oscillators (all waveforms can be activated simultaneously)
• Oscillator B with 2 low modes
• hardsync
• Noise generator
• mixer
• 24dB Lowpass filter
• 2 ADSR envelopes
• 1 LFO with sync
• Arpeggiator
  
• Step sequencer
• Modulation bus
• Assignment for aftertouch
• Handwheels for Pitchbend & modulation
• Pedal input for expression or footswitch
• MIDI In / Out / Thru
• USB MIDI
• Headphone output
• Main Out (mono)
  

With the FOURM, Sequential presents a polyphonic analog synthesizer with SCI Prophet-5 and Pro-One DNA and a contemporary sound character. The FOURM is not only very similar to the Sequential classic Prophet-5 on the outside: the typical signal path consisting of two oscillators with simultaneously activatable waveforms, mixer, Lowpass filter, VCA and envelopes has been retained and adapted to today's needs in harmonious details such as the feedback circuit. The modulation options also go beyond those of the "P5", as the overhauled modulation bus from the SCI Pro-One is used here. The 37-key slimkey keyboard is equipped with polyphonic aftertouch, making expressive playing a pleasure. Thanks to the shortened keyboard, the FOURM is extremely compact and weighs just 4 kilos. The synthesizer can be played polyphonically in four voices, alternatively there is a fat unison mode and the option to play monophonically. As a classic playing aid, the editable arpeggiator is of course a must and a polyphonic step sequencer is also on board. The FOURM lives from its great basic sound alone, ultimately the sum of all components contributes to this, but above all the modulation bus with AT assignment, which creates sounds that the historical original from 1978 cannot master.

The first thing that catches the eye is the visual proximity to the and Pro One with a contemporary sonic character. Externally the FOURM closely resembles the classic Prophet 5, and its typical signal path of two oscillators with simultaneously selectable waveforms, mixer, lowpass filter, VCA, and envelopes has been retained and updated with thoughtful details such as an enhanced feedback circuit. The modulation options also go beyond those of the original P5, as the redesigned modulation bus from the SCI Pro One is integrated here. The 37 key slim keyboard features polyphonic aftertouch, allowing highly expressive performances. Its shortened keybed keeps the instrument extremely compact and lightweight at just 4 kg. The FOURM provides four voice polyphony, a powerful unison mode, and the option to play monophonically. Classic performance features include an editable arpeggiator and a polyphonic step sequencer. While the FOURM is impressive for its overall architecture, it is the modulation bus with aftertouch assignment that enables sounds far beyond what the 1978 Prophet could achieve.

The FOURM has four primary modulation sources. The two crisp ADSR envelopes are permanently assigned to the filter and VCA. The synchronizable LFO with four simultaneously activatable waveforms is assigned in the modulation bus. The (polyphonic) aftertouch section can modulate up to three destinations simultaneously, which are divided into the groups frequency OSC A/B, cutoff/amp, LFO frequency/amount.
The modulations are assigned on the left of the control panel. This is the modernized form of the modulation bus from the from 1981. The filter envelope, oscillator B and the LFO, each with its own attenuator, are available in parallel as sources. These are assigned to the targets Frequency Oscillator A+B, Pulse Width Oscillator A+B, Cutoff, Amp, LFO Frequency and LFO Amount via buttons. The color coding provides information about the modulation links. Red or blue means from one source to one or more destinations; purple has 2-3 modulation sources.
Used carefully, wild oscillator drifts, sync sounds, sirens, FM for filters and/or oscillator A as well as pulse width modulation are possible. Turn it all up at once and it gets really wild!