Understanding Harmony: Part 2


Having already looked at major and minor scale triads and the primacy of I, IV, and V chords, we'll now look at chord inversions and the difference between three- and four-part harmony, before touching on a number of other highly useful chords that every songwriter should know about. I’ll also try to illustrate some really useful tried and tested harmony writing techniques that include things like suspensions and pedal points. These appear time and again in all the best songs!

The study of harmony involves chords and their construction; chord progressions and the principles that govern them”

Chord Inversions and Alternative Chord Voicings

The seven major and minor C scale chords listed in Part 1 were all written in ‘root’ or ‘close’ position. In other words, the intervals between the bottom and middle, and middle and top notes were either major or minor thirds.

Any triad can be inverted simply by placing the bottom note at the top. With a three-note chord, this can be done twice to create different chord voicings. A third time simply moves the whole ‘close position’ chord up an octave. Moving the bottom note to the top once creates a ‘first inversion’. Doing it a second time creates a ‘second inversion’.

Here’s how this works taking a simple C major chord as a starting point:

C major inversions

From this illustration, we can see that a first inversion chord has an interval of a perfect 4th at the top, whereas the second inversion chord has the perfect 4th at the bottom.

In fact, there’s no reason why any of the notes of our C major triad should stay together in close position. Here’s an example of the above same chords written with expanded intervals to create a different texture. Note, however, that they are still recognizable as root, first and second inversions.

C major inversions wide

Three and Four Part Harmony

Why is four-part harmony so much more commonly used than three part harmony? The answer to this is probably historical; a great deal of choir music has been written for a four part combination of soprano, alto, tenor and bass voices (SATB), plus the string section of the symphony orchestra is generally comprised of a violin section divided into 1st and 2nd violins, plus a viola and cello (and bass) section. To write for this combination of instruments certainly means writing at least four independent harmony parts.

Moving from three to four part harmony means that one of the notes in any triad must be doubled. It also means we’ll need to move to a ‘grand stave’ or treble and bass clef bracketed together, in order to have room to write out all the parts.

Which note to double is a subjective decision and depends on the musical context, but here are some general observations:

  • Doubling the tonic is very common, especially when the low note is played on a different instrument such as bass guitar. The ‘right hand’ chord could be in root position or any inversion, of course. 
  • Doubling the fifth is also very common; this frequently occurs if the whole chord is a first inversion chord. 
  • What about doubling two of the notes? Doubling the tonic and third notes while leaving out the fifth altogether is OK at times.
  • Doubling the tonic and fifth note while leaving out the third is possible, but since the third defines whether the chord is major or minor, the chord will be a bit ‘ambiguous’ – which may be just what’s required! 

Here’s how some of the above options look in written out form in D major; I’ve also included the guitar chord notations that are commonly used to describe them:

D major 4 parts

In the above illustration, you’ll notice I’ve tried to keep a nice wide gap between the tenor and bass notes. There’s no rule that says you have to do this but low notes close together often tend to create a ‘muddy’ texture.

Pedal Points, Seventh and Suspended Chords

Any root position triad can be turned into a seventh chord by adding the 7th note of the scale to the other three notes in the chord. By far the most common type of 7th is the dominant 7th or V chord which always wants to take us back to the tonic or home key.

The dominant 7th has a minor 7th as its widest interval. It works because the top note is actually the fourth note of the scale, which always tends to want to fall or be resolved onto the third note of the scale.

Another example involving the fourth note is the suspended fourth chord, which substitutes the 4th note in place of the third. Theory textbooks sometimes say that because of the dissonant clash between the 4th note held or suspended against the 5th, there is a need to resolve the suspended chord by letting the 4th fall to the more consonant 3rd note, but for some time now it has been fashionable in pop music to let some suspended chords just ‘hang’ unresolved, depending on the context.

A pedal point is a useful common harmonic effect. The term simply means a single note (often a bass note) is held for a period of time against moving harmonies. This creates dramatic tension that is resolved when the pedal note ends.

The short piece that follows demonstrates several points we’ve covered; the use of a pedal point, suspended 4ths that do and don’t resolve, the use of 1st inversions, a secondary 7th towards the end, and a ‘bare fifth’ open chord at the end (no middle note to the triad). Listen to it as an mp3 and try to follow the written score below as it plays.

Guitar strings piece harmonies

The music score above is the basis of what actually happens in the piece once the rhythmic movement of the guitar is taken out.

Note the pedal note is an F. In fact, as the harmonies move it combines with the G chord to form a dominant 7th in the key of C. Perhaps it is hard to spot because the 7th is in the bass, but this is actually just an inversion of the dominant 7th. Being a 7th it wants to resolve downwards and in fact does so twice.

Diminished Chords

I should also touch on the diminished seventh chord briefly. In our original C minor scale list of triads, we saw that both the supertonic and the 7th (sometimes called the leading note) form triads that are diminished chords because the interval between the bottom and top notes of the chord is a diminished 5th, if you keep to the notes of the scale of C minor.

Now take the ‘leading note’ chord and add a 7th, still keeping to the notes of the scale. Our diminished chord now becomes a diminished 7th. Let’s look again at the C minor scale and the triads formed from it, this time with guitar chords written in and the diminished 7th added:

C minor diminished triads

Suspended 2nd and 'Added Note' Chords

Guitar players have exerted an enormous influence on modern rock music, not just in terms of sound but also the chord shapes that naturally lie ‘under the hand’. These have become part of the style of the harmonic language itself.

Suspended chords, as we noted above with the suspended 4th, are used often without resolving the 3rd. Added or suspended 2nd chords are also frequently used. A suspended 2nd chord is similar to a suspended 4th, except the 2nd is either substituted in place of the third instead of the 4th.

An added 2nd plays just as it sounds, the normal tonic triad has a 2nd added to it. This adds colour and variety to the chord. The piano riff piece that follows has plenty of examples. Try to follow the simplified score along with the mp3:

Piano riff piece harmonies