The Series-of-Fifths Progression: The triads in a key can be arranged as a series of downward fifths, I-IV-viio-iii-vi-ii-V-I (in major). This pattern is strongly goal oriented because the roots of the chords move to successive interval roots, creating a domino effect among the roots of the chords. The one exception is IV-viio, a tritone movement (VI-iio in natural minor).
A third relation can be used to enter a series-of-fifths progression at any point in the series-of-fifths pattern. The next three examples illustrate how upward and downward third relations can be used to set a starting point in the series. The first few chords are used establish the tonic pitch. The substitution coincides with the beginning of the series-of-fifths pattern.Example 7: Downward Substitution To Enter A Series-Of-Fifths Progression.