Hi Bernie

in as much as I understand the Nord manual, in particular page 34 , you should set the lower Channel to e.g. channel 4. This should correspond to your setting of the Korg as described on my webpages:
GLOBAL EDIT MODE>> PAGE 7: MIDI IN CONTROLS: chord 1 : midi channel 4

Then I you should set the Midi Channel ( is the main channel on the Nord) completely OFF.

In this way you should have the Korg acc. on the lower keys of the Nord,
the upper sounds of both instruments on each respective upper half .
At least that would be my way of reasoning.....

I am off now, speak to you tomorrow.

John