How Chords Progress
There are three basic PROGRESSIONS. (Other movements are RETROGRESSIONS.)
- Down a 5th
- Up a 2nd
- Down a 3rd
In describing root movement by intervals, we will consistently refer to the downward 5th, which lands on the same pitch as the upward 4th, but there is no reason to call this movement by two different names. Likewise, a 3rd down is equal to its inversion, a 6th up.
In addition to these three basic movements, a chord may progress to the tonic (I) or dominant (V) at any time. Thus, the vi – V movement is common, as is the ii – I movement. Both are considered retrogressions. The leading tone 7th (viiº) typically moves to the tonic (I).
Chords can be grouped into three basic families. These are the Subdominant, the Dominant, the Tonic. The Subdominant if often called the Predominant. They tend to move in this fashion:

Either of the two chords in each family may be used, and progressions follow the root movements described earlier. For example, consider the root movements in this progression:

The movement is down a 3rd, down a 3rd, up a 2nd, and down a 5th.