Interval Between Roots of Chords: Intervals between chord roots fall in four categories; seconds, thirds, perfect fifths and the tritone. Each category includes the interval and its inversion (i.e., a perfect fifth down and a perfect fourth up belong to the same category). Second, third and fifth relations refer to the interval between roots of chords.
Some melodic intervals, including those between chord roots, produce the impression that one of the notes is the root of the interval. Movement toward this root produces closure (movement toward a goal). Movement away from the root has an opposite effect (movement away from a goal).
These effects are most pronounced in perfect fifths and major thirds. It is quite instructive to test this hypothesis by playing and singing melodic intervals repeatedly to judge on one of the notes makes a better note of repose than the other. The closure effect applies equally to melodic intervals in melody and between roots of chords.Example 1: Closure In Melodic Intervals