Originally Posted by jmattbassplaya
IME, scales make really horrible fills.
Do you mean note-to-note scales make horrible fills? Because most fills are scale-based in some fashion. This is one of those areas that some players have a tough time implementing - the difference between a note-to-note scale and choosing notes from a scale to create a fill. One of the most simple fills comes from the simple I IV V progression:
| C | F | G7 | fill: g a b
and back to C. This is hardly a horrible fill, but nor is it terribly interesting.
The key to creating a good fill is to choose notes from a scale (such as a minor pentatonic) and craft the fill using various intervals within the scale rather than just regurgitating the scale from scale degree 1 to 2 to 3 to 4, etc.
To aid in this scales should be practiced in all manners of intervals. The most simple variation is:
1 3 2 4 3 5 4 6 5 7 6 9 8. Repeat in reverse.
Then create all sorts of permutations, such as:
1 4 2 3 2 5 3 4 3 6 4 5 4 7 5 6 5 8 6 7 6 9 7 9 8. There are many more you can create to make things more musical.