Hi ericbrad
P250 is a beautiful keyboard though as it has 88 pianotype keys will be harder to play pipe organ literature.....
In fact I did some xperiments with my older Korg SG1D 88 and a single sustain pedal, using EMU x-midi simple Midi/usb cable to my similar win7 x64 T4400 dual core laptop.
Hehe, it is possible to get superb sound and some good functions to help in a live situation.
After you study these tutorial videos and do your homework (needed !!) then you can :
Set SP250 to transmit to midi channel 2 (usually default for the great manual or hauptwerk or grand orgue ect)
I'm assuming you'll use at first a simpler 2m/p sample set like Vendaam, or indeed the superb Demo organ which comes native with the program !!!!.
In GrandOrgue also set the great manual to receive in ch2,
swell/positiv in ch 1
Pedal in ch 3
Then, use the positif to great coupler to add stops to the great as will be the sole manual available there. Or you can have it always on and get all Grt and Sw stops as one division.
Now the pedal. Use your sustain pedal to engage disengage the Pedal to Great coupler found in extra couplers permantly in use as native functions in GO software.
Assign your sustain pedal (right click, wait for event ect) to use it as on / off, so you'll get great bass for your left hand when needed. Also you can use the monophonic version ie only the lowest notes will sound with pedal ranks/stops.
Here this setup works very well indeed and you can also use your extra keys from your Korg as physical stops (right click on stop, press the appropriate/as your taste key on Korg then set toggle, so the virtual stop will stay on until deactivated from a second press of the key)
You can assign also general pistons to your extra keys. And you can get a kinda real organ image, if you assing the virtual stops as are in the sample set, left and right.
I mean, since the lowest note on the majority of organs have C1-036 and top on treble from C5-84 or D5-86 or E5-88 or F5, G5 up to C6-96, you're left with no more than 28 stops control (in a 61 keys manual), 13 on the right and 15 on the left ;-)
There are real positive/continuo organs that indeed they use the real keys for stop levers ! like the Purcell Major, which it comes with one manual 61 keys, but its compass is up to F5-89, then G5, A5, B5 and C6 are 4 stop "levers" for engaging/disengaging 8', 4', 2'2/3 and 2' respectively. Then it has more : The F#, G# and A# are tuning switches (415, 440, 468) Cooool, so we can model such a setup with just a 61 keyboard, imagine now with your 88 !!
The easiest way to get a top sound with no latency is to use Asio4all (free), do not forget this. Midiger is not using Asio at all.... only Directsound and native windows driver.
But to get to this point you really must do your homework on how to use grandorgue software to 100%
Have real fun !
best
Panos