Dominant Seventh Chord: How Interval Forces Work

The dominant seventh chord has some remarkable properties. Compare Figure 54 above with Figure 55 below:

FIGURE 55: Interval Forces

The dominant seventh chord contains the first note of all three of the most highly unbalanced intervals—scale degrees 2, 4, and 7; and
The tonic chord (scale degree 1) contains the second note of all three of these intervals—scale degrees 1, 3, and 1 (8). Figure 56 above shows the interval forces created.