I would strongly suggest you use them as two seperate keyboards. It is way much easier and it will save you a lot of aggravation in testing it out the other way.

I tried this with my Tyros and a KN2600. Not only did I want to do as you mentioned, but to be able to switch back and forth quickly and easily between songs etc.

Guess what. It is not even remotely worth trying out.

On top of that I tried to use the voices from the Tyros in the Technics styles. While it did sound pretty good once gotten there again it was very, very difficult to do.

IMHO you would do well to just drop the idea.

If you can't resist and would like to play around with this out of curiosity, I would love to hear of you experiences. Hopefully they would be a lot better than mine.

Scott