Justforfun,
actually Ketron lets you save both the style and the arrangement; you can modify a style (for example, if you don't like the instruments assigned to the lower part) and then save it, or you can create an arrangement, starting from a style and then choosing different instruments for Acc, Bass, Drums, Upper, Lower, Effects, etc and then save the result as an arrangement. Usually these will be saved to the hard disk, but you can choose to overwrite the arrangements and also the styles written in ROM. At least, that's what I always do. Ketron also keeps the original styles in a separate folder, labeled "Reload", so if you by mistake erase a style you can always reload it from the hard disk into the ROM.
It's not easy to grasp at first (every keyboard has a different "logic"), but once you get it, it's even easier than on other keyboards.
Andrea