Native Instruments B4 II - Manual (Page 47)

B4 II – 47
On the resulting menu choose Set Upper Keyboard Split to define the upper
split point. This key and all above it will play the upper manual from now on.
The keys below it play the lower manual.
Similarly, use the menu entry
Set Lower Keyboard Split to set the split point
between the bass pedals and the lower manual.
When Keysplit is activated, the split points are shown with markers on the
upper manual in the Keyboards View.
To delete your keyboard splits, right click again on the upper manual and
choose
No Keyboard Split from the resulting menu.