This appears to be a DCO multi-paraphonic design of some kind. Standard presets for Ensemble and Solo that can be mixed and auto-accompaniment patters typical of early Yamaha PS/PC keyboards and the like. This one just uses preset DCO analog synth architecture. Probably one VCF for solo and ensemble sections.
Typical problems with Korg Poly type panasonic key movements. Glazed contacts etc. Rub down with acetone until cotton gets black. Measure w/probes and it should be under 1000 ohms with probes pressed side by side on rubber conductive surface. If all else fails order the contact disks from the keyboard parts page and stick them on and it'll work like new.
I have the VCF chips
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