Just set up the four sounds that you want with a particular style and save to Songbook!
Don,
I might be missing something here...but...
Korg might show a keyboard set of four of whatever.
Let's say I trade keyboard set #2 which might be a whistle and make it a piano. When I save it to songbook, the whistle choice shows whistle but plays piano...fine.
Here's the thing, when I'm using lyrics, I have to remember that whistle now = piano. Can be a bit confusing.