I've mentioned in a previous Forum Discussion on how to create this in the primary level of Reaktor 6. Creating a Key Hold option.
Absynth when it was available had Key Hold function.
DESCRIPTION FOR KEY HOLD FUNCTION: Whatever keys you hold down on the keyboard will remain active, even after you lift your fingers. Even in polyphonic additional notes you play will be added to the keys/chord currently playing. Playing new keys will turn off currently playing notes and replace them with the new notes you play.
Can any programmer elaborate on making this? Correctly in polyphonic mode.