The issue is that if you use OTS link, when you change the Variation (A-D) the RH sounds change immediately and if you are HOLDING RH notes during that...oops it messes up your performance. (That is assuming the RH voice you are playing DOES change with the OTS) IF you do not use OTS link OR if you use registrations THEN you have full control as to when the sounds in the RH change. Then they change when you press the OTS or the Reg.