You can get there a bit with Yamaha's Style assembly, in that you can take a bass line from one style, and insert it into a different one...this also applies to the other style parts like drums, phrases, pads, chords.

This is by far the easiest way to create another style, as the parts are already set up to work...no note limits to set, no NTR or NTT to figure out, etc.

The newer Yamaha Style Creator also allow for stroke or arpeggio for the guitar parts.

Style creator's Groove & Dynamics lets you easily set the amount of "swing" for a style, or sections of that style. it also has other uses that I won't go into here, but suffice to say, the average player can do quite a bit of editing without knowing a lot of technical info.

I'm sure Roland and Korg have very similar features and perhaps some that are more extensive and even easier to use.

As I said earlier, most people who see it being done, or have it explained properly (I often used Skype) rematrk at how easy it was.

Ian