[DarkStar]

You need to make sure that the MIDI from the keyboard is getting to Kontakt - there is a checklist in the Reaper User Manual. It will be easier to sort that out if you disable Kontakt and add Reasynth to the track.

Then make sure that the MIDI channel of the notes from the Kurzweil keyboard is the same as the channel for that instrument in Kontakt. You can use ReaControlMIDI to monitor (log) the MIDI messages from the Kurzweil keyboard.