ACC parts/Lower up down button:
for ACC parts when Arranger modo
for Lower when Organ modo
Lower voice can not use in Arranger modo.
Upper 1/2 button:
select 1 or 2 with other button
My opinion for EM-50:
Good option as Style Player
Not so good for Pro musician performing use.
Sound Quality= Good with external audio System. Internal is weak.
Effect= Reverv, Chorus only