With Yamaha, you can move that left hand voice up the keyboard well beyond the split point, thus use it as not only a left hand layer, but also a lead voice for your right hand.
Neat feature,
Gary
And not just on Yamaha, but on KORG as well - can't speak for other brands as I have not owned them ...
More often than not, my left hand voice is an Organ ... It provides some fullness and some counter melody when I want ...
Three right voices and one left voice are all independent of each other, so setting volume controls etc. is very easy ...
I would assume Yamaha works in a similar way ?