Having fully established the foundations of tonal harmony, we are now ready to expand our studies to include chromatic harmony, so this unit will be our first introduction of functional accidentals–meaning altered notes that are critical to the function of a chord as opposed to non-chord tones accidentals that are only used to embellish other pitches. As you read on, remember that all tonal harmony relates back to the function and voice-leading that we established in studying basic diatonic harmony.
To this point in our curriculum, we have spent the majority of our time studying the primary functions in tonal harmony–tonic, dominant, and pre-dominant chords–as well as the ways in which we can extend primary functions through the tertiary functions of cadential, passing, pedal, and arpeggiated chords. The observant among you will notice that we have skipped secondary function, but we are now ready to study chromatic harmony and therefore introduce this missing concept. Secondary dominant chords, a small set of chords with secondary function, will be our starting point because they are a logical extension of circle-of-fifths progressions.
Before we add chromaticism, let’s establish a voice-leading standard by harmonizing the following progression in four-part harmony. Because it is full of root position triads, you may need to use incomplete chords to create smooth voice-leading while avoiding errors.
In Unit 7, we discussed the evolution of the circle-of-fifths progression, and in that process, we saw that the circle-of-fifths progressions are strong because the voice-leading closely mirrors a series of V-I progressions. With that in mind, let’s zoom in on the middle measure of the ii-V-I progression that you completed above. (This will work for any voicing that you chose, but I have inserted the voicing that I used in the next example.) On the staff below, I have isolated the ii and V chords in the first two measures. In the second measure, I have copied all of the voices exactly from the first measure, but I have altered only the key signature to match the tonic of the second chord–in this case, our second chord was the V chord, a G major triad, so I used the key signature for G major without altering any of the voices. Analyze the second measure in G major while taking into account the new key signature. What progression have we created?
As you can see, these two progressions are identical with the exception of one accidental. The ii-V progression in C major has a weaker pull than the V-I progression in G major, but they are functionally similar. Therefore, we could strengthen the ii-V progression in C major by adding one accidental to the ii chord to have it mimic the dominant chord in a secondary key. To try this, take your completed progression from the first example above and alter the one pitch necessary in the ii chord to “steal” the dominant chord from G major. (I have provided you with my voicing if you deleted yours, but feel free to copy your voices into the appropriate lines of the ABC notation.)
To steal the chord from G major, you only need to raise the third of the ii chord to create a D major triad–the V chord in the key of G major. This creates a temporary V chord instead of a ii chord. You can hear the finished product in the following example.
For a brief moment, the progression is acting as if a non-tonic chord–in this case, the V chord–has become the tonic. We call this tonicization, and this is the first example in our studies of secondary function. Tonicization is one of those rare logical names in musical theory because we briefly treat a non-tonic chord as if it were a tonic. And for those wondering, this is not modulation; we will discuss the difference between the two in the upcoming Unit on modulation.
Primary function stems from the voice-leading in our standard circle-of-fifths progressions, and the dominant-tonic relationship acts as the basis for all diatonic tonal harmony. As mentioned in the introduction above, tertiary function chords extend the function of the primary chords on either side of them. Secondary function chords are different because they can stand on their own and substitute for a primary function chord. In the example that we created above, we replaced our standard ii chord by substituting a V chord from a different key.
Remember that when using Roman numerals analysis, it is best practice to explain any chords that do not have their “standard” function. If a I chord has a dominant function, such as a cadential I 6/4 chord, you should denote in some way that this particular chord is tertiary function rather than the I chord’s standard tonic function. If a viio6 is not acting with its standard dominant function and instead acting as a passing chord, that should be noted in your Roman numerals. Secondary function chords are no different.
In the example above, the ii chord transforms into a major chord once the sharp is added, so it is no longer a “standard” ii chord. To denote this in our Roman numerals, we use two Roman numerals separated by a slash: V/V. We read this as “five of five”. In this labeling, the Roman numeral before the backslash is the chord’s function as if it were in the key of the Roman numeral after the slash. In our example above, the D minor chord becomes a D major chord, so it now acts as the V chord in the key of G major: a “five of five”.
One important note, standard practice for secondary function chords allows you to tonicize any chord that is not a diminished triad. This means that viio in major and minor as well as iio in minor should not be tonicized.
Because we label secondary functions in Roman numerals using slashes, students often confuse the function of the slash with leadsheet symbols. In leadsheet symbols, a slash denotes an inversion to the chord by denoting which pitch is in the bass voice, where in Roman numerals, we use inversion figures to denote the bass note. A slash in Roman numerals implies a secondary function and tells you what key is being tonicized. While both systems are useful for theorists, you must be careful not to let the nomenclature mix together.
In our progression above, what would happen if we had decided to use a ii7 chord instead of a ii chord? Try it on the following staff. Start by harmonizing the ii7-V-I progression below while making sure that you resolve your chordal thirds and sevenths correctly. Once you have a voicing that you like, alter the ii7 chord using accidentals to create a V7 in the key of G major – a V7/V (read: “five seven of five”)
When you alter the ii7 chord in the same way that you altered the ii triad to create a secondary dominant, you create a secondary dominant seventh chord–in this case, a V7/V.
There are many possibilities for using these beyond tonicizing V chords, because any major or minor triad can be tonicized by a secondary dominant seventh chord. Instead of altering the ii chord in the above progressions, try altering the vi chord. What chord will it tonicize? Which accidentals will need to be borrowed? What will you call it once you have altered it? We will fully examine these ideas in Unit 15.