Properties

You might have noticed that the cadential 6/4 chord was the only 6/4 chord included in the harmonic functions table. That is because it initiates a dominant function. Therefore, it can follow either a tonic- or predominant-function chord. However, it is highly unlikely to follow another dominant chord. The cadential 6/4 resolves to either V or V7, which prolong dominant function.

The diagram below shows an example of the cadential 6/4 in a progression.

I	IV	cadential 6/4	V	I
T	P	D	[D]	T

The cadential 6/4 chord is the only 6/4 chord that is consistently used in an accented metrical position compared to its resolution.

Label

Different institutions and textbooks teach and label the cadential 6/4 in different ways. Some use the label "I6/4," since the chord is spelled like a second-inversion I triad. (If writing this label, you should also write "cad" below the label to indicate the chord's use.) Others simply use the label "cad6/4."

The cadential 6/4, however, should be understood as an embellishment of the V chord, not as a tonic triad. A third way of labeling the chord more accurately reflects this. What follows is a step-by-step process toward understanding the third, preferred, label.

In the example below, we see ii6 moving to V. Notice that in the top voice, F skips down to D, leaving a space of a third. Similarly, the second-to-lowest voice leaves a space between D and B.

We can fill the space in the top voice by placing a passing tone on E. The Roman numeral below the staff shows "V6—5," which refers to the motion above the bass: the sixth above the bass, E, moves down to the fifth above the bass, D. (Important: In this case, "V6" does not refer to a first-inversion V triad! Rather, it indicates a V chord whose fifth is momentarily displaced by a sixth above the bass.)

Finally, we fill in the other space with a passing tone on C. Like in the second measure, this creates motion above the bass, specifically a fourth moving to a third (4—3). Put together, these two passing tones create simultaneous 6—5 and 4—3 motion above the bass, resulting in figures that look like 6/4 and 5/3. Notice that we didn't change the Roman numeral, because the E and C are understood to be embellishing tones above the V chord. (For this reason, it is crucial to include the lines connecting 6—5 and 4—3. Otherwise, the label will look like a V in second inversion followed by a V in root position.)

In the example above, the "V6/4—" label (with the dashes) refers to the cadential 6/4, and the "—5/3" label (with the dashes) refers to the V chord to which it resolves. Therefore, we can refer to these two chords as "the cadential 6/4 and its resolution."

Points of clarification:

There may be one or more additional octaves between the bass and the notes of the cadential 6/4. Still, we simplify by saying "sixth" and "fourth" regardless of octave placement.
- For instance, the sixth may appear as a thirteenth (or greater) above the bass. Similarly, the fourth may appear as an eleventh (or greater) above the bass.
The sixth and fourth above the bass do not have to be in specific voices. They may appear in either the soprano, alto, or tenor.
The sixth may appear in a lower voice than the fourth.

Resolutions

The cadential 6/4 can resolve to either a V triad or a V7 chord. As described above, the sixth and fourth above the bass resolve down when moving to a V triad (6/4—5/3). When moving to V7, there are two possibilities. The example below shows the octave, sixth, and fourth above the bass moving down to the seventh, fifth, and third, respectively (8/6/4—7/5/3).

The example below shows another possibility. Because the fourth above the bass is dissonant, it must resolve in a specific way (4—3). Because the sixth is consonant, however, it is free to resolve upward instead, to the seventh (6—7). This example also shows how the bass note may change octaves during the cadential 6/4's resolution. The octave change can also happen with the resolutions described above.

Part-Writing

As illustrated in all the examples above, the note in the bass is doubled in the cadential 6/4 when writing in four voices. If part-writing from a given set of Roman numerals and figures, resolve the notes of the cadential 6/4 according to the figures. Then, resolve the V or V7 as normal.