Like earlier posts, this is more Wersi vs. Ketron related but if you an SDxx series Ketron:

Let’s take the next step. In an earlier video, we showed that we were able to play styles and sounds from an external MIDI device (in our case a Ketron SD40) from the upper manual of our Sonic.
While that is interesting I’m sure most folks that own a Sonic would prefer to play not only the upper keyboard but most likely the lower keyboard and the pedals – You know, like a real organ!
In our next video, we are going to scratch the surface of how you can play both keyboards of the Sonic and play sounds and styles in the Ketron. In future videos, we will build on that solution and add in Wersi sounds with the Ketron sounds.
https://youtu.be/EBvXfRboTzs