What to you think is inside your closed arranger ?
All keyboards are powered by a computer with an OS.

The terms Closed Keyboards and Open Keyboards are defined by their ability to be expanded by the manufacture and the end users outside their original factory state.

You buy a Tyros 3 today and it does what it does. Never anything more than that. Hence why it's a closed system.

You buy a Mediastation and it's technically unlimited in what it can do. Henc why it's an open system.

The CPU and OS do not define Closed and Open keyboards.

My OASYS is a Linux PC and I can't install anything I want on it. I can only do whatever KORG intended it to do.

Regards
James