Is many ways to do, is all depending on skills, tools, instument.
Professional musicians like do this directly on arranger.
Other like to just get it, load it and play

I believe many people want to know how this work, where to start..etc
I've been there. 7 months ago I didn't have a clue how can be done.
All my live I was very into Midi and now since I have KORG Pa600 I using my knowledge to enjoy very powerful, great Arranger.
Thank You KORG for flexibility.
I develop many ways to do styles, some easy and poor, some very hard but with great final effect.
I decide to help a little creating some basic tutorial.
Is not like perfect method, I know better ones, but showing on Fl Studio is giving chance to beginners see basics info how this work.
In future, if I find some extra time I planning to do Advanced Style Creation tutorial for more advanced users.
Feel free to ask any question.
So far I hope somebody will learn something.

Making Korg PA Arranger Style on FL Studio
PS. I you see any errors or something I miss it, please let me know. I been doing this in the middle of many different things and I am only Human.