Now here's one of my favourite pieces, played by Michael Witek in 2014 on a Tyros 5. What I find really interesting about watching Michael play this piece is that he has 'split' his keyboard in two places. He does have a 76 note keyboard which enables him to do this. Had it been any less he wouldn't have had enough notes in each part of the split to do anything meaningful. As it is, you can hear (and see) how he has brought those two 'voices' into his piece.
Of course one could do something like this by 'multi-tracking' and putting the counter-melody in afterwards, but there is something to be said for being able to play a piece like this 'live'.
Tears In Heaven
Hugh