According to lore, we know it can sing you a song. So naturally, the top half must be the man and the bottom half is piano
Also he needed to play a harmonica too so that also suggests top half man bottom half piano.
The song about the piano man includes a harmonica but thereโ€™s no indication that he uses one.
Can a piano not sing
It can if the top half is human
maybe it is a more advanced version of the Mark Rover talking piano?