I understand Joost's suggestion and it's a good one. In the architechture of the WK style engine, you can actually program three completely separate fills for each variation - major, minor and seventh. The intention is that you will hear a different fill depending on what type of chord was being played when you hit the fill button. Even if your song only uses major chords, you only need to quickly hit a minor of seventh chord before you hit fill and that will trigger a different fill. The fills themselves don;t have to be minor or seventh in tonality. You can program whatever you like in there. Using this system will give you a total of twelve fills available; three for each variation.

Also, if you tend not to use the Intro function, you can also use this as an extra fill. When pressed it will trigger the pattern you programmed, (again, three patterns per variation are available), and return to the normal riff when finished.

Chris