Lesson 26- Secondary Dominant Triads

In Lesson 15, you learned what dominant triads were and how to form them. You should review that lesson if you are unclear about such triads, because a clear understanding of dominant chords is essential to create what we call secondary dominants.

By way of a brief review, you know that dominant chords are built on the fifth degree of a scale, and must be major in quality. This is because in a dominant chord, the 3rd of the chord acts as a leading-tone to the tonic. For example, in C-major, the dominant chord is a G-major chord. The 3rd of the G chord ('B') is a leading-tone to the tonic. And the most important feature of dominant chords is that they "point to" the tonic. To use the vernacular, they "sound like they want to go to" the tonic. The root of the tonic chord is a fourth above, or a fifth below, the dominant, and that's the chord that the dominant wants to move toward. Study and listen to this example:

  Listen to the progression:  

  Listen to the 3rd resolving upward:  

This much should be common knowledge to you, as it was covered in Lesson 15. You should note that it is not essential for the V-chord to resolve to a I-chord; it would still be a V-chord no matter to what chord it resolved. If a V-chord moves somewhere other than the I-chord at a cadence, that would produce what is known as a "deceptive" cadence- for obvious reasons!

So that explains dominant chords. What about secondary dominant chords? Secondary dominant chords make a note other than the tonic sound like a tonic. Study this progression:

    

It is the ii-chord that we want to focus on here. In the major key, the ii-chord is always a minor chord. But what if we purposely change the ii-chord so that it is a major chord? We would do that by raising the 3rd of the chord- by making the 'F' an 'F#'. The result would look and sound like this:

  

The D chord, which is now major, presents a bit of a "surprise" to our ears. In our western culture, we are very quick at picking up tonality. Even with just the first two chords, we hear the key of C-major as a strong possibility. We expect a minor chord when we hear a chord whose root is based on the second note of that scale. This is a cultural response, not an academic response. So when we hear a major chord whose root is the second note of a scale, it's a bit unexpected. But despite its unexpectedness, our ears tell us something right away about that chord- that the minor quality has been changed to major for the purpose of creating a leading tone. Specifically, the 'F' has been raised to 'F#'. The F# sounds like a note that wants to resolve upward.

You can readily see that the D chord now has the same characteristics as those of a dominant chord: 1) it is major, possessing a leading tone that wants to resolve upward, and 2) its root is a fifth above, or fourth below, the resolution chord. For now, a question mark has been placed under the chord in the graphic below: since ii-chords must be minor in a major key, and this chord is now major, we have to find a new name for it, which we will later in this lesson:

  

In the two ways that matter, this "major ii-chord" operates as if it were a V-chord. If it were a V-chord, what chord would it be trying to make sound like a tonic? Since V-chords make the chord whose root is a fourth higher (or fifth lower) sound like the tonic, we would say that it is a V-chord of the V-chord. The proper way to indicate this is with the following symbol: V/V. When we see V/V, we say, "five - of - five". When we say "V/V", we know that we mean a ii-chord that has been adjusted to be major. A V/V is a type of chord that we call secondary dominant.

So a V/V makes the V-chord sound, even just very briefly, like a tonic chord. In fact, many composers use V/V, or other secondary dominant chords, to change the key of a piece of music, what we call "modulate". If you wrote a piece in C-major, and decided that for interest's sake you would modulate to G-major, a V/V might be a chord you would choose to make the G-chord sound like a tonic instead of a dominant.

Here are some chord progressions. The progressions in the left hand cells of the table use ii-chords. In the right hand cells of the table, the ii-chords have been changed to V/V, by making the ii-chords major. Play each example and make certain that you can hear the difference.

Here is a iii-chord in Bb-major:    As you can see, it is a minor triad. Here is that same triad, modified so that it is now major:    The note 'F' has been raised to 'F#'. Our ears hear that the purpose of this raising is to create a leading tone. If 'F#' is acting as a leading tone, to which note is it leading? 'F#' is a leading tone to 'G'. In our key (Bb-major), a G-chord would be a vi-chord. So the D-major chord is acting as a dominant of the vi-chord. We would label that chord: V/vi and call it "five of six". Here are two progressions, one using a iii-chord, the other using a V/vi in its place:

Do you hear that changing the ii-chord to a V/vi, by making it major, increases the chords "desire" to move to the vi-chord?

There is one other naturally-occuring minor chord that we can change to a secondary dominant: the vi-chord. By making a vi-chord major, we create a secondary dominant to the ii-chord:

It is of course quite possible to create secondary dominants in minor keys. Simply take any chord that naturally occurs as something other than major, make it major, and you will have created a secondary dominant. Here is an example:

In the first example, the i-chord leads quite nicely to the iv-chord. However, by changing it to be a major chord (raising the third), you create a secondary dominant, a chord that even moreso wants to resolve to the iv-chord. The second example takes the ii-chord and makes it major creating a secondary dominant V/V.

SUMMARY

We have seen that we can take the three naturally-occuring minor chords from a major key - the ii-chord, iii-chord, and vi-chord- and create secondary dominant chords by simply making them major. We can do the same changes in chords from a minor key. Our ear hears them as behaving like dominant chords because we hear the raised third degree that wants to move to the root of the chord a 4th higher or fifth lower, just like dominant chords do. When we change the structure of a chord in this manner, the name of the chord must change. To call something a ii-chord means that the root of the chord is based on the second degree of the scale and that it is minor. By making it major, it cannot be a ii-chord anymore. Some people are tempted to simply call it a II-chord (i.e., they use upper-case for the number) but this is not correct. It must be renamed in the manner shown in this lesson.

Before taking the quiz for this lesson, try the following quick exercise. Rewrite each bar in the blank bar beside it, changing the chords shown with an arrow into a secondary dominant triad. Give the Roman Numeral Analysis for each chord. (Assume that each excerpt is in the major key according to the given key signature. Then click here to check your answers. (Will open in new browser window)