The PS-3100 Analogue Synthesiser has monstrous polyphony - one built-in VCO, VCF, VCA, and EG for each of the keys on the keyboard for a total of 48 synthesizer circuits and polyphony! There is no Ring Modulator or "tremolo modulator"; it has only 12 (divide-down) VCOs; there are 2 LFOs; and patch memory didn't exist in 1976.
The PS-3100 has a rich sound despite its single VCO (triangle, saw, square waves, plus PWM) and its LPF is warmer than the MS synths. The Resonator (3 bandpass filters) can create formants and phase effects. LFO1 has a range up to 1khz, multiple wave forms, and can create FM effects using AM, which is continuously variable right up to Ring Modulation. There are 2 EGs - one polyphonically affects the VCA and LPF, the other (General Envelope Generator) is universal and paraphonic. The GEG can also be widely used as a modulation source. It has12 scaling controls for non equal-tempered intonation. There is an Ensemble for 70s style string patches and an extensive patchbay. The PS-3100 is huge, weighs 30kg and Korg made only 600. In 2009 you could expect to pay approximately USD 4500 / EUR 3500 for one.
Its successors, the PS-3200 and PS-3300 have far greater potential, but the PS-3100 is the only one which is built as a single compact personal synthesizer with its built-in keyboard. The modules are completely separate and inter-connected using Korg's standard patching system. You create sounds by patching and twisting knobs, very similar to Korg's MS-series.
Demos & Media
Images from Switched On Music Electronics.