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Section 1

Chord Changes with the Primary Triads

Movie 9.1  Root movement by an upward
fourth or downward fifth

Movie 9.2  The tonic-subdominant pair share the same characteristics as the dominant-tonic pair.

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The most important of these other chord changes is that from the tonic to the subdominant (i.e., from the tonic triad to the triad built on the fourth note of a major or minor scale). This is because the tonic chord’s position relative to the subdominant is the
same as that of the dominant to the tonic – the only difference is that the movement is away from the tonic rather than toward it.

The I, IV, and V chords, then, share a unique and symmetrical relationship. These three, which we earlier called the primary triads, are the main connecting points of a chord progression Chord Progression A series of harmonic changes or chords, either within a key or changing from one key to another. The strongest type of chord movement is that in which the roots of the two chords are separated by a fourth or fifth, as they are in the tonic-dominant pair — especially a rising fourth or descending fifth. The primary triads, the tonic, dominant, and subdominant chords, share a unique and symmetrical relationship, wherein the tonic has the same relationship to the subdominant as the dominant has to the tonic. These three are the most important chords in a standard progression.

Popular music, such as the twelve-bar blues progression, is often built exclusively on the I, IV and V chords. – the big cities, so to speak, on your harmonic highway.

For much of popular music and even many well-known classical themes these are the only chords you need to know. The power of
the cycle between I, IV, and V is well illustrated in the standard twelve-bar blues progression, which works exactly the same way
in hundreds of compositions.

Movie 9.3  A typical blues progression uses only the primary triads

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Adding a new dominant after “I won’t be back at all” would take us back to the beginning of the cycle, which can repeat indefinitely. Having the chord cycle remain constant allows the musicians to add melody and accompaniment without losing even inexperienced listeners.

The blues progression illustrates the tension between predictability and surprise that is at the heart of effective musical structures. The conventions of the progression provide a framework for innovation, and also establish a model of predictable behavior that can be altered from time to time with great effect. Perhaps the most important of these conventions in tonal music is the journey from the tonic to the dominant and back again. Compare the blues progression to the beginning of this Mozart Piano sonata:

Mozart’s piece is certainly different in style from the blues, but is still based on the same logical interplay between the three strongest chords: tonic, subdominant, and dominant. Harmonically, the two examples have much in common, at least in the first
few measures.

Movie 9.4  I, IV and V in Mozart’s Piano Sonata K. 545

Suggested Practica Musica Activities 9.1

• Analyzing Primary Chords: Identify primary chords by roman numeral.
• Hearing Primary Chords: Identify primary chords by ear.

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Harmonic Rhythm

You may have noticed that the chords in both the previous examples change much less frequently than the notes do. This is true of most tonal music based on accompanied melody: we say that it tends to have slow harmonic rhythm. In most pieces, the underlying chord – the one that “goes with” the melody – will change only once a measure or at the most, twice, unless the
piece is very slow.

J.S. Bach’s famous chorales, short vocal works for four voices,
are often studied for their harmony. The chorales could be said to have a fast harmonic rhythm, since they change chords on almost every beat:

Movie 9.5  J.S. Bach: Herzlich lieb hab ich dich, o Herr

Review 9.1

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Section 2

Extending the Dominant-Tonic Relationship

Root Progression By Ascending Fourth

The idea that chords follow each other well if their roots are a fourth or a fifth apart can be extended to the secondary triads.
None of these changes has quite the strength of V-I or even I-IV, since they all begin with minor chords and therefore have no leading tone, but they still have a trace of that dominant-tonic relationship. For example, ii moves very nicely to V, iii to vi, and vi to ii. You can even string together a chain of such chords, as in “Heart and Soul.” This kind of progression, in which roots move by ascending fourths or descending fifths (vi, ii, V, I), is sometimes called a circle progression Circle Progression A progression of chords in which
roots move by ascending fourths or descending fifths (vi, ii, V, I). It’s called a circle progression because it follows the path of the circle of fifths.

As a general rule, root movement of
a rising fourth or descending fifth is strong and effective and may be repeated without limit. because it follows the path of the circle of fifths.

Movie 9.6  Progression by fourths and fifths

Movie 9.7  Progression by chain of fourths in “Heart and Soul”

This repeating chord progression is based on chord roots that move by ascending fourths and descending fifths.

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Progressing Backward

Though a sense of resolution is strongest with the root movement of a rising fourth/descending fifth, there is still
a strong connection when the movement is by a descending fourth or rising fifth: I often moves to V, of course, and
IV to I. Similarly, you may see vi-iii, ii-vi, or even V-ii, as
in the Bach chorale of Movie 9.5.

Root Movement by a Third

Another extension of the basic chord progression principle comes from the fact that triads whose roots are a third apart sound related, since they always share two notes.

Of the two possible ways to move by a
third, the descending direction seems to
be the stronger, perhaps because ascending
movement leaves the former root behind.
The stronger descending movement can
effectively be repeated at least twice in
succession, as in I-vi-IV.

Movie 9.8  Progression by thirds

Figure 9.1  Chords whose roots are a third apart have two notes in common
and can serve similar functions. In most cases the root of the substitute chord
is a third below rather than above the chord being replaced.

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Chord Substitution

Because chords whose roots are a third apart have two notes
in common, they can serve similar functions and you can often substitute one for the other (see Figure 9.1). A good example of this is the frequent use of vii° in the place of V, as illustrated in the Bach chorale below. Another example is the "deceptive" resolution of V to vi, with vi substituting for the expected I.

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Movie 9.11  The II chord functioning as a dominant to the V chord

Movie 9.12  Using the dominant seventh chord to
make an even more convincing secondary dominant

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You can convert any of the triads in a key into secondary dominants, except the IV chord in a major scale or the
VI chord in a minor scale. Why can’t those chords function as secondary dominants? Because there’s no scale note a perfect fourth above them. For example, the IV chord in
C is built on F, and a perfect fourth above F is B♭, which
is not in the C scale. So there’s no note in the C scale that could use F as its dominant.

Movie 9.13  Secondary dominant chords in the key of C major

Suggested Practica Musica Activities 9.2

• Playing Secondary Dominants: Play the secondary dominant
for a given chord in a given key.

• Chord Progression Ear Training: Use Roman numerals to
identify which chords are played.

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Modulation

Secondary dominants are one means of giving the impression that the key has changed and that a new tonic has been established.
If the new tonic is confirmed by further chord changes it could be said that the music has modulated to a new key. If the passage
in the new key is lengthy, a key signature might be displayed to mark the change, but often the change of key is accomplished using accidentals alone. Modulation Modulation A chord progression that takes us
from one key to a newly established key. Secondary dominants are often used to establish a new tonic.

Modulation to another key may be indicated by a change of key signature, but not necessarily. Modulation usually occurs between closely related keys, ones that share some of the same chords. The function of the shared chords will change as the shift is made from the old key to the new key; the
V chord in C major becomes the
I chord in G major, for instance. We call this common-chord modulation. is usually made to a key that is closely related to the previous key, that is, to a key that shares
some of the same chords. The composer can then modulate by common-chord modulation, changing the function of one of the
shared chords so that, for example, I of the old key is now IV in the new key, as in Movie 9.14. This makes a seamless transition
to the new key.

The chord progression principles described here are not intended to define all that is possible in harmony. They’re a way of describing what tonal composers have usually written in simple pieces. By following these principles your music has a better
chance of pleasing you in the same way that you have been pleased by other compositions.

Movie 9.14  Common-chord modulation in Bach’s Chorale 160, Gelobet Seist Du, Jesu Christ

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The Chord Progression Game

The concepts described in this chapter can be summarized in two charts that we will call the major and minor “chord boards.”
The “chord boards” are for playing a sort of composition game. To play, you start with any one of the circles numbered “I” for tonic, and then you move to other circles to build a chord progression. Your last chord should be another I, preferably preceded by a V.
The thicker lines are an extra help; they indicate the stronger type of movement. The strong line from vii° to I shows that vii° is
used like V to return to the tonic. As in most board games, you can move only in certain ways:

Rules

• You can move along any of the lines that connect chords. Most of the
time this means you can move either horizontally, vertically, or diagonally.

• You can’t skip over chords.

• You can move horizontally rightward any number of times consecutively,
but in any other direction only twice consecutively.

• At any time you can jump to a chord
of the same name (if you’re on a ii spot you can jump to any other ii). This is needed if you reach an edge of the board.

• You can alter a chord to a secondary dominant (that is, make it major and maybe add a seventh) but if you do,
it should be followed by the chord to
its immediate right.

Movie 9.15  Sample chord progressions made following the game rules

The chord boards take no account, of course, of the greater concerns that motivate composers, but they are a fun way to experiment with harmony.

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Review 9.2

4. Secondary dominants are possible for any triad
of a given key, except for the IV chord in a major
key and the VI chord in a minor key.

5. The harmonic change that takes us from one key
to a newly established key is called modulation. Secondary dominants are often used to establish
a new tonic.

6. Modulation to another key may be indicated
by a change of key signature, but not necessarily. Modulation usually occurs between closely
related keys. If the transition is accomplished
by use of a pivot chord both keys share, it is called common-chord modulation.