Four Voice

Back in 1975, this synth made history as the first true commercially available polyphonic instrument, letting players lay down full chords with four independent voices instead of wrestling with monophonic beasts like the Minimoog.

It pairs four SEM modules—each a mini-synth with dual analog VCOs offering sawtooth, pulse (with PWM), and triangle waves—to a four-octave keyboard (49 notes, C to C) that scans digitally for reliable polyphony. A standout 12dB/oct state-variable filter per voice switches between low-pass, high-pass, band-pass, or notch modes, modulated by dedicated filter EG, LFO, or external CV, while two EGs and LFOs per SEM handle pitch, pulse width, and more. The optional Polyphonic Programmer stores 16 patches with coarse but effective resolution, and built-in dual eight-step sequencer, mixer for per-voice volume and stereo panning, plus polyphonic portamento add serious creative punch—all housed in a sturdy Tolex-covered cabinet with cream aluminum front panel and black knobs.

Players still chase these for their thick, organic depth from SEM variances, though maintenance can be a labor of love due to vintage components. Prince turned its brassy leads and effects into classics on early albums like For You.