The older MIDI based styles used a "map to C7" routine, much like many musicians, okay, maybe Pianists, think when they are transposing to a different key. \

Let's say, for example, you wanted to play a song that you can easily play in C, but now want to play it in G. Well, any C note would become a G note, any D would become an A, etc.

I think there's a little more to it than that "under the hood" though, what with software, algorithms, that sort of thing, but the mapping to C7 is a major part of rolling your own style, said the man who once forgot to do that routine when trying to make his own style...