Now we will address non-circle-of-fifths progressions. Notice that we have not included the \(\left.\text{vii}^{\circ}{}\right.\) or \(\left.\text{IV}\right.\) chord in any of the shorter circle of fifths progressions above. However, it is a common axiom that Rock ‘n’ Roll is made up of three chords: \(\left.\text{I}\right.\), \(\left.\text{IV}\right.\), and \(\left.\text{V}\right.\). This is because each of those chords represents a harmonic function. Harmonic function refers to the tendency of certain chords to progress to other chords, or to remain at rest. Many texts on music theory enumerate three harmonic functions. In this text, we will discuss four.

1. Tonic function (abbreviated “ton.”): The \(\left.\text{I}\right.\) chord has tonic function, which is a state of stability and rest. Tonic chords do not demand progression to other chords.

2. Dominant function (abbreviated “dom.”): The \(\left.\text{V}\right.\) and \(\left.\text{vii}^{\circ}{}\right.\) (chords containing the leading tone \(\hat{7}\) and supertonic \(\hat{2}\) ) tend to progress to tonic (\(\left.\text{I}\right.\)). Special note: The \(\left.\text{I}\middle/\text{5th}\right.\) chord has dominant function when it resolves to the \(\left.\text{V}\right.\) chord, as in the third chord from the end of the “Star-Spangled Banner.”

3. Pre-dominant function (abbreviated “pre-dom.”): The \(\left.\text{IV}\right.\) and \(\left.\text{ii}\right.\) (chords containing the subdominant \(\hat{4}\) and submediant \(\hat{6}\) ) tend to progress to chords of dominant function

4. Tonic prolongation function (abbreviated “ton. prol.”): The \(\left.\text{vi}\right.\) and \(\left.\text{iii}\right.\) (chords that share two common tones with \(\hat{1}\) –\(\hat{3}\) –\(\hat{5}\) from the tonic triad) tend to occur after the tonic chord and progress to chords of pre-dominant function.

Harmonic function is represented on a flowchart in the next section.