>Step by step
Exploring harmonic function
1 OK, so let’s start off in familiar territory with our old friend, the C major scale – seven notes, played on the white keys of the piano keyboard, starting on C and going up the keyboard through D, E, F, G, A and B, before concluding on the higher C, an octave above our root note of C. 2 The notes in the scale are known as degrees. If we stack alternate notes onto each degree to produce three-note chords or triads, we end up with the following set of diatonic chords (ie ‘belonging to the scale’): C, Dm, Em, F, G, Am and Bdim. Note the last chord ( Bdim) is a diminished chord. 3 As well as the regular chord names, we can label these diatonic chords with Roman numerals that describe their position in the scale and also whether they’re major or minor. Upper case numerals denote major chords, while lower case denotes minor or diminished chords. This helps describe progressions without being confined to a specific key. 4 These chords can be grouped into different function ‘families’ – that is, groups of chords that can perform a similar function within a progression. Let’s look first at our I chord – C major in this case. This first chord in the diatonic set is known as the tonic chord, since it’s rooted on the tonic of the scale – C. 5 The tonic function represents a feeling of ‘home’ or rest in a musical setting – if a progression is a journey, the tonic is the natural end point that all the other chords are leading back towards. The I chord’s tonic function is shared, although to a lesser extent, by the iii and vi chords – Em and Am in this case. 6 The dominant function, the second of our chord families, is all about tension and forward motion. Dominant chords have a natural tendency to want to resolve or pull back to the tonic, creating a sense of relief from the tension. Chords that have a dominant function include the V and vii chords – G and Bdim in this case.
7 The final chord family is the predominant group, whose task it is to bridge the gap between the tonic and the dominant chords, extending the progression in a more interesting way than just using tonic and dominant chords alone. The IV, ii and sometimes the vi chord can all have predominant function ( F, Dm and Am in this case).
8 Let’s look at a few examples, beginning with the basic tonic to dominant progression. I’m using T to stand for tonic, P for predominant and D for dominant in these examples. Left open-ended, a TD - progression or ‘phrase’ like this one leaves the listener wanting and expecting more music – it just doesn’t sound finished.
9 Stick a T on the end of the phrase for the dominant to resolve back to, and it suddenly sounds much more satisfying – although a bit short. We can extend it by bunging a P in between the two to get a TP-D-T phrase – C-F-G-C – a pretty common progression found in thousands of tunes.
10 Making a progression longer by inserting extra chords is known as prolongation, as we’re prolonging the inevitable return to the tonic via the dominant. In our next example, we’ll start with a move from the tonic to the iii chord: C to Em. This is known as a tonic prolongation, as the iii chord’s tonic function prolongs the sense of rest.
11 We can prolong the tonic function even further by moving to the vi chord next – Am in this case – after which we could move to a predominant: say, the IV chord, F major. We can prolong the move to the dominant even further by following this with a ii chord: Dm, another predominant chord.
12 Taking the Dm as the start of a classic 2 - 5 - 1 turnaround, we can now stick in our dominant V chord. After all this prolongation, we’re crying out for a resolution back to the tonic, which we get in bars 7 and 8 with a return to the I chord, C major. This completes our T-T-T-P-P -D-T phrase.