I though you might be interested to know that I've just added another mod to my MP4. I've added portamento to the filter cutoff keyboard tracking. It is controlled by the same portamento knob as the oscillators. And that without adding any new circuits or components. Just re-routing some control voltages.

I've simply disconnected one wire (pin 1) on connector 18 of KLM-355C (filter board) that was bringing the keyboard CV coming from KLM-356D to the filter. And installed a new wire connected to the left side of R202 on KLM-354 to connector 18 (pin 1). Effectively taking the keyboard control voltage of VCO 1 and using it also as filter keyboard follow. So the glide times are identical to that of VCO 1.

Anyone interested to make this modification, just drop me a line, and I will show you exactly how to do it. It involves having some experience at soldering wires, and possessing a good welding iron (pen type).There is no risk of "overloading" the CV signal from VCO 1 since the input of the filter keyboard tracking CV is buffered by an op amp of very high impedance.

Korg should have added a portamento feature to the filter cutoff in the first place (as on many Moog synths).

Alain.