Back in 1978, this French oddball arrived as one of RSF's rarest rackmount gems, with only about 200 units made, packing two voltage-controlled oscillators that could smoothly morph between waveforms like triangle, square, saw, and pulse— a trick that set it apart from the Minimoog-inspired crowd.
Housed in a surprisingly light 3kg 3U chassis despite its beefy looks, it delivers monophonic subtractive synthesis through dual analog VCOs with sync options, a standout 24dB/octave lowpass VCF based on the SSM2040 chip that self-oscillates with bite, two ADS envelopes, and a versatile LFO offering triangle and square waves for modulation duties. Hands-on control comes via around two dozen knobs and switches for real-time tweaking of oscillator mix, filter resonance and cutoff, envelope curves, and LFO rate, plus patch points for CV/gate integration and external audio processing through the filter and VCA. A mono audio out and 16 onboard memories round out the essentials, making it a compact core for semi-modular rigs when paired with the Expander II's extras like ring mod and sample-hold.
Vintage enthusiasts chase it for that raw, characterful tone—think Jean-Michel Jarre vibes—praising the waveform morphing and filter saturation, though its scarcity and age mean tuning quirks keep techs busy.
