This synth sounds FAT. It’s architecture is really simple, but it sounds really good. I can’t think of any 80s polysynth that is better at making fat, Moog-ish leads and basses. Six voices of a patch like that sounds absolutely huge. It has the 4 way joystick shared by the whole Korg “Poly” series which effectively gives you an extra (analog-controlled) LFO. The oscillators have a lot of low end and can sound really fuzzy, like Big Muff fuzzy. It has a simple arpeggiator that allows you to tell it to run your arpeggio up and down the whole keyboard. If you trigger an arpeggio by playing several notes in different octaves, it will alternate steps above each of them as it arpeggiates, allowing you to make some complex, interesting sequences.
This synth suffers from the same NiCad rechargeable battery leak issue as many of its contemporaries. This particular one had had this happen, and it had been cleaned up, years ago, but was still suffering the aftermath. The alkali from the original battery had caused corrosion on various pin connectors. Someone had replaced the battery with a new NiMH rechargable battery which they had decided to just wire to the battery solder points on the board with wires about 10 inches long, so it was just knocking around in there.
Work Done: it arrived with the fuse for the +5V (digital) supply blown, and I never confirmed the reason why, but it was probably because of the aforementioned loosely flapping battery’s wires shorting against something, or the panel boards all being missing numerous screws, causing them to flap around against each other/the panel as well. I replaced this fuse, recapped the power supply, put in a board-mounted CR2032 holder and necessary diode to block charging current. There were two intermittent voices, for different reasons. One was due to corrosion on the SSM 2056 EG chip’s socket; the other was due to corrosion on a pin connector on the CPU board that sends the gate voltage over to the envelope generators, preventing that voice’s EG from being triggered.