When I did this, I used a Roland E50 as my lower KB because I strongly prefer Roland's "Chord Intelligence" to Yamaha's AI Fingered. I made a special rubato style for the Roland that turned one or two played notes into triads and tetrads, which drove the Yamaha's style engine. I preferred the Yamaha's RH voices, and seeing an animated score display on the color screen.

It was a great setup. But that A-frame with all the wires made my living room look like a music store. So I scrapped it for a Tyros 5, ably assisted by a Roland module. Much neater, but far less functionality. And all this because Yamaha was too proud to copy the highly logical simplified chording system that Roland had already figured out. Shame on them! Someone needs to make Steve Deming write 100 times on the blackboard "one finger equals a major chord"!!