I have just checked it on my psr.
Reg buttons can bring ACCMP on and off but they need to save a style with at least one reg button.
Press the reg1(e.g.) button to call the appropriate voices
Disable accomp (press accomp button to shut down)
Choose a style
Press memory button
Mark the style box
Save reg1 (e.g)
Try these things how it can be done with the Genos screen "butons" and if you can do what you want or not.
Other way is to have the split point in far left position and "loose" only one key.
Remember to save a test copy of the reg then "push" buttons on -off etc to see if you(or anyone else) can archieve what you want to avoid the always boring manual reading.
Children don't learn their first knowledge by reading books, they just smash things down first
Always a copy of a style,midi,reg etc and "smash" it to see how it works.