In diatonic harmony, second-inversion chords do not function in the same way as other inversions. Whereas root-position chords are stable, and first- and third-inversion chords create momentum by placing tendency tones in the bass, second-inversion chords are generally considered “weaker”. For example, listen to the following sonority repeatedly. It contains both a P4 and P5 above the a root. Because there is a dissonance between the upper two voices, you will likely hear this as wanting to resolve in some way. Isolate the voice that you would like to resolve and then figure out how you are naturally resolving it by singing it.
Most people will resolve this sonority as if it were a root position major triad that has a suspended third, although some might hear this as a minor triad instead. The P5 seems more stable as opposed to the P4. These resolutions would sound like this:
Conversely, if you were to hear the P4 as the more stable interval, you would resolve the P5 upward to create a second-inversion triad in either major or minor.
Not only are these examples effective in demonstrating your ear’s natural inclination toward root position, but they also show the basic diatonic underpinning of for limiting the use of second-inversion chords. In the above example that resolved the original sonority to an F major/minor chord, you can see how closely-related any key is to the key of its subdominant. Therefore, if used incorrectly, second-inversion chords can destabilize your part-writing by pushing toward a different key.
Because second-inversion triads are not as stable as the other inversions, they must be used differently in your part-writing. Instead of fulfilling a primary function such as tonic, dominant, or pre-dominant, they will have one of four alternate functions:
For each of these functions, the chord will be extending the primary function of another chord rather than defining its own.
As a general rule, 6/4 chords function best when the bass voice is doubled. As you harmonize the chords in each of the examples below, notice how often this doubling occurs naturally in your part-writing.
A cadential 6/4 chord is the most straightforward usage of second inversion chord, because it has the most specific rules.
Harmonize the following three examples to see how well the voice-leading works for a cadential 6/4 chord.
Cadential 6/4 progressions are often used to correct part-writing errors in approaching the V chord. Look at the third progression that you just harmonized. If the cadential 6/4 were removed, it would create parallel perfect 5ths between the soprano and bass.
Some theory methods teach that a cadential 6/4 should not be labeled as a I6/4; instead, they label it as a V6/4 - 5/3. The reasoning behind this is twofold:
These reasons enforce an understanding of the true nature of the cadential 6/4. I prefer to label it as a I6/4 chord, however, because:
Passing chords are the second alternate function for second-inversion chords, and they function identically to our description of how first- and third-inversion chords are used as passing chords–a chord inserted between two other chords to create a bass line with stepwise motion. As before, passing is a function that replaces a chord’s primary function, and instead extends the function of the chords on either side. Harmonize the following example of a passing 6/4.
Understanding that the ii chord in this example acts as a passing chord rather than a pre-dominant chord also explains how a V chord moves convincingly to a ii chord. When a chord resolves against the normal flow of a circle-of-fifths flowchart (see Unit 7a), we call that a regression. In the example above, the first V chord should resolve to a tonic chord but instead regresses to a ii chord. This works because of the strength of the bass line, so it is the passing function that extends the dominant harmony through a stepwise bass line.**
Now that we have practiced using a passing 6/4 chord, we can also clarify why viio6 chords function well as a passing chord. When studying first inversion chords [Unit 11b]](/inttheory18-19/11-further-part-writing/b1-voiceleading1stand3rdinv.html), we discussed two important ideas regarding viio chords:
This explains why a viio6 chord functions as a passing chord; it is actually a functional substitution for a passing V6/4 chord. Harmonize the following two progressions to see how similar these two chords are.
Like the cadential 6/4 and passing 6/4 chords, the pedal 6/4 is defined by the motion that it creates in the bass line. A pedal 6/4 occurs when the bass line remains static across multiple chords by employing a second inversion chord. Note that this is different from a non-chord tone pedal, because a pedal 6/4 chord uses only chord tones to create the static pedal; it does not use non-chord tones to create the pedal. Harmonize the following two examples of common pedal 6/4 chords.
The fourth and final acceptable usage of 6/4 chords occurs when the bass line arpeggiates through a chord. When part-writing arpeggiated chords, you will not have stepwise motion unless you use non-chord tones, because the chord tones will either remain static or skip between chord tones. Try the following example, and you will see how this requires voices to jump between chord tones.
The most common question regarding arpeggiated chords is how to handle them in your analyses. Depending on the harmonic rhythm of the piece, an arpeggiated chord may be viewed as either a melodic bass line that does not change inversion or an entirely new instance of the chord in a different inversion.
Your decision should ultimately reflect how you hear the piece. If you have a repeated harmony but each reiteration of the harmony sounds like a new phrase or statement, then you should label each inversion of the chord according to its bass note. On the other hand, if it sounds like one continuous harmony, particularly if a melody and phrasing implies this, then you do not need to mark every inversion of the chord.
Regardless, you should label the chord’s inversion by the strongest note in the bass. This will often be the lowest note in the arpeggiation, but your perception can shift depending on the order in which you hear the arpeggiation as well as which pitches are in the strongest metric position. Take time to listen to the passage carefully, and choose the pitch that most closely reflects your perception.