Hi synth experts! Here's a web find that spoke to me. It's one of the better demos I've heard of the rare RSF PolyKobol synthesizer. I've always been somewhat preoccupied with the rare and the weird, in synths as I am in automobiles. While relatively mainstream car enthusiasts lust after the right vintage of Porsche 911 or Ferrari, I'm daydreaming of a Citroën DS or Venturi Atlantique. Those are both French, and so is RSF.
Most serious synth geeks consider the PolyKobol (and yes, there was a mono predecessor called simply the Kobol) the ultimate unattainable in synthesizers. Moreso than a perfect Yamaha CS-80. Moreso than an Elka Synthex. Moreso than a Gleeman Pentaphonic with the clear plexiglass housing.
Unique for the PolyKobol's era was the ability for oscillators to morph between waveforms in real time. Today, we take for granted the idea that the "waveform" knob can be a modulation destination, but in the early 1980s, Wolfgang Palm's PPG was the only other manufacturer to be implementing anything similar in a polyphonic "slab" synth -- albeit in a very different way i.e. the digital domain with wavetable oscillators. The RSF PolyKobol, by contrast, is fully analog.
It had the well-known temperature-induced issues with stability, but one in good shape is truly something special. This video from YouTuber seb17320 shows that the sound lives up to the mystique.
Fortunately, XILS-Lab are as weirdness obsessed as I am, and they make a virtual instrument emulation that has received accolades even from those who've encountered the real thing.