I think a lot of arranger players get too attached to doing things like registration changes with their hands, whereas watch most organ demos, they are doing things with their feet.

Technically, you SHOULD be playing so much that taking your hands (and mind) off the playing would compromise the music. I find putting registration changes on a footpedal keeps my hands on the keyboard, my groove intact, my head in the music. A simple ‘Performance Up’ and ‘Performance Down’ pair of footswitches can turn a complicated dance of stopping playing with either hand, pressing the correct button (often from a row of similar looking buttons, sometimes quite some distance from the keybed!) and returning to the keybed in perfect time with the perfect notes into the simplest task for a foot…