What Notes Do I Play?

The first hurdle of creating new runs is to determine what notes to play.  The question is not as difficult as it seems, for there are but a few guidelines to follow:

1. If it is in the chord, it works.
2. If it is in the scale, it probably works.
3. If it is not on the scale, but is moving to a note on the scale or in the chord, it should work.
4. If it sounds good, it works.

Based on these fairly open-ended rules, you should quickly realize that anything can become a run or fill, as long as it sounds good.  Now I realize that these rules are rather abstract, so let us look at some concrete examples of them in action.