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Chord Progressions

Chord progressions are simply sequences of chords. Chord progressions are often written with roman numeral notation instead of with pitch letters, allowing chord progressions to be described independent of the key they are played in. There are three fundamental concepts you must know to understand and compose effective chord progressions: the V - I progression, chord substitution, and voice leading.

V - I Chord Progression

One of the most common patterns in chord progressions is the descending fifth — the movement from one chord (the "V" chord, also called the "dominant" chord) to another chord with a root note a fifth below (the "I" chord, also called the "tonic" chord). For example: from G to C, or from F# to B.

NOTE: These chords can be played in any inversion. Though we are descending a fifth to find the I chord in a V - I progression, the I chord does not need to be positioned a perfect fifth below the first chord and does not need to be in root position.

A particularly common form of the V - I progression is the V7 to I (or, in minor keys, V7 - i) progression. In major keys, the V7 chord consists of scale degrees 5, 7, 2, & 4, and the I chord consists of scale degrees 1, 3, & 5.

The V7 chord is tense because of the dissonant tritone interval between scale degrees 7 and 4 (the 2nd & 4th notes of the chord) and because it contains the leading tone (the 7th scale degree) which strongly leans towards the root note of the scale:

V7

The I chord releases the tension because it resolves the tritone by moving the leading tone to the scale's root note, and moving the 4th scale degree down to the 3rd scale degree to form a major 3rd:

I (2nd inversion)

This dominant - tonic resolution can be used between scale degrees other than 5 & 1 as well. For example, another common chord progression is II - V - I, which works because II is the dominant chord of V (because scale degree 2 is a perfect fifth above scale degree 5), and because V is the dominant chord of I. So, a II - V - I chord progression is essentially two successive V - I chord progressions:

ii (2nd inversion)

V7

I

Just about every chord progression there is can be analyzed in terms of V - I progressions when combined with the next important concept: chord substitution.

Chord Substitution

Chord substitution is simply replacing a chord in a chord progression with a similar chord. Chords are considered "similar" if they share many notes or if they resolve in similar ways to the next chord in a chord progression.

The simplest chord substitutions change only one note in a chord. A common way to change one note in a diatonic chord is to instead use a diatonic chord up or down a 3rd.

In C major, for example, the I triad consists of the notes C, E, & G:

I

The iii triad, a 3rd up from I, consists of the notes E, G, & B, which shares the E and the G with I triad:

iii (2nd inversion)

The vi triad, a 3rd down from I, consists of the notes A, C, & E, which shares the C and the E with the I triad:

vi (1st inversion)

Because both the iii chord and the vi chord share 2 of 3 notes with the I chord, they can both substitute for the I chord, and they are all categorized as "tonic" chords. The same can be applied other chords that are a 3rd apart, like the ii & IV chords (considered "pre-dominant" chord because they generally lead to "dominant" chords), the V & vii chords ("dominant" chords), and so on.

You can create more complex chord substitutions changing more than one note in a chord, adding notes to a chord (forming extended chords), or removing notes from a chord.

NOTE: You do not always have to replace chords with similar chords in chord progressions — you can also add additional chords to chord progressions instead.

Important Chord Tones

One thing to keep in mind when using chord substitution is that some chord tones are more important than others in giving a chord a specific sound and harmonic function, and these important chord tones may be worth preserving in substitute chords.

The two most important notes in any chord are the root and the 3rd. The root is important because it lays the foundation for chords — we can't have a C chord without a C! The 3rd is important because it determines whether the chord is major or minor, which plays a huge role in how the chord sounds.

Beyond the root and the 3rd, the 7th is the next important chord tone because it determines the type of 7th chord that is formed. Next are chord extensions — the 9th, the 11th, and the 13th. The least important chord tone in most chords is the 5th because in most cases it does not play any role in determining the type of chord that is formed.

NOTE: Though the 5th is not an important chord tone in most chords, it is important if it is altered in some way — for example, the #5 in an augmented triad, or the b5 in a diminished triad.

Voice Leading

The last fundamental concept you must know to understand and compose effective chord progressions is voice leading, which is the arrangement of the notes in chord progressions (called "voices") to create smooth, flowing transitions between chords. Good voice leading can make just about any set of chords work together in a chord progression.

The most important rule of voice leading is to use the smallest possible movements when moving the voices of one chord to the next chord.

Take the V7 - I chord progression in C major (G7 - C) as an example. One way we can voice these chords is by playing both of them in root position, with the C chord below the G7 chord. These root position chords are an example of ineffective voice leading, because each voice in the G7 chord has to jump a long way to the corresponding voice in the C chord:

• G moves down a P5 to C
• B moves down a P5 to an E
• D moves down a P5 to a G
• F moves down a P4 to a C

Contrast this with a better example of voice leading, where V7 is in 2nd inversion and I is in root position, allowing for small movements between the voices in each chord:

• D moves down a M2 to a C
• F moves down a m2 to an E
• G does not move at all
• B moves up a m2 to a C

You can hear that this voicing is much smoother, because the individual chord voices move small distances.

NOTE: Large jumps in the bass voice (the lowest notes) of chords are sometimes acceptable, as they are more pleasing to the ear than large jumps with other chord voices. The example below illustrates this: both the V7 chord and the I chord are in root position, and the bass voice jumps down by a P5, but the chord progression still sounds good.

Interactive Exercises

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