I don't think an aranger keyboard is what you are looking for. Arrangers are for general use - they can address a variety of styles acceptably well for live performance. It will do everything from Jazz to Hip-Hop, but the styles you mention seem pretty specialized.

I would suggest you look into a program called Fruity Loops. It is a loop-based composing program which emulates a hardware instrument called a "beat box." I have only tried it cursorily. If you search with Google you can find other groups that explain this unit and other hardware and software devices suitable for techno. You should be able to find a demo of Fruity Loops also.

Good luck, and please describe "Orchestrial." This is a term I have not heard.