With respect Donny, no it doesn't make much difference at all. The harmonisers look for a chord pattern, NOT the octave it is played in.

The harmoniser algorithms are designed to recognise roots thirds and the altering notes, sixth and seventh.

I could play a ten finger chord and the harmoniser will still only apply the correct harmony note/s according to the basic chord shape.

What DOES affect the sound is the number of voices, usually up to four, and the timbres chosen...Don't mistake the low sound in a harmony for playing a low note on the keyboard. Check and you will find it is a voice set to a bass timbre..

With my PAx's I usually set all the harmony voice timbres and octaves to flat, or 0. This gave the most realistic results, as did setting the harmony to close.

I played chords on the keyboard in full piano mode and in arranger split mode (chord rec on upper or lower depending on the song) and I did not notice any difference on the harmonies generated.

Dennis