Guitar Lesson #6 - Pedal Point
Pedal Point (also called "Pivoting") is a technique where you keep returning to some base tone called the "Pedal Tone," for instance:
32, 31, 37, 36, 35, 34, 33 (always returning to 3)
21, 27, 26, 25, 24, 23, 22 (always returning to 2)

The idea of Pedal Point could also be extended to where the "base" that you're returning to is some musical motif rather than just a single note.
Pedal-Point Guitar Solo, minor scale audio example: