Registered: 04/28/06
Posts: 837
Loc: North Texas, USA
Depends on the fingering mode. Which, in turn, depends on the chords in the song, and especially whether there are any slash chords. Somewhere between F#3 and C4 (counting C2 as the lowest note on a 61-key board.)
Note that Yamahas define the split point as the HIGHEST note in the accomp section; Rolands define it as the first/lowest note of the Upper part.