Third Relations: A third relation progression, up or down, has a static property because the progression contains two common tones, indeed three common tones if seventh chords are involved.
If no tones are altered, triads in a third relation are always of different types. Thus, an important property of this progression is a change in chord color. Harmonic focus and linear movement are secondary to color change.
A progression of a minor third (up or down) produces little harmonic closure, partly because of the common tone effect, partly because it is difficult to judge which note of a minor third is the root of the interval.Example 3: Effect Of Third Relations