Stringing It All Together

Previously, we talked about harmonizing major scales to discover which chords occur naturally in a key. Now lets find out what harmonic area each chord sits in. A harmonic area is essentially the overall feel of certain chords related to their parent key. We call these areas Tonic (stable, pleasant to sit on), Dominant (unstable, wants to resolve to tonic area) and Pre-Dominant (stable, but a nice bridge between dominant and tonic). Because tonality prioritizes pitches in a certain way, notes and chords in a key will have contextual habits.

Here are the functions of each chord in a key. Minor keys act a little differently depending on whether you’re working with natural or harmonic/melodic minor. For simplicity’s sake we’ll be working in a major key. Remember that each chord is named for its scale degree. For instance, in the key of C major – C D E F G A B – we’d call the chord built off of C the I chord. The chord built from D would be the ii, and so on.

Tonic Pre-Dominant Dominant
I, vi vi, IV, ii, iii V, viio

These functions are the same whether we’re using triads or seventh chords. The exception would be viio; it becomes a minor 7-flat 5 chord (half-diminished) which is typically pre-dominant.

So a typical progression in the key of C, would be I (C major), IV (F major), V (G major) back to I. You’ve probably heard something like this a quadrillion times. That’s because these chords have a tendency to want to go together, in that order: Tonic -> Pre -> Dominant -> Tonic. Some other possibilities are:

  • Tonic -> Dominant -> Tonic
  • Tonic -> Pre (vi for example) -> Pre (IV) -> Dominant
  • Tonic -> Pre -> Tonic (we don’t even need a Dominant!)
  • Tonic -> Dominant of Dominant -> Dominant -> Tonic (more on this one at another time)

Pre-dominant chords like to follow each other in a descending numerical fashion. If we want to put a few pre-dom chords before reaching our dominant chord, vi moves nicely to IV. IV can go to V or continue to ii first. If we go backwards from ii -> IV -> vi, it sounds a little weird. The iii chord is kind of weak and thus typically wants to move to one of our stronger pre-dominant chords before going to a dominant; like a (pre)pre-dominant.

When we want to end a chord progression, the final move is referred to as a cadence. In most music, we find cadential movement at the very ends of musical phrases. There are a number of types of cadences, depending on the context. Very generally speaking, they fall into these categories:

Type Example
Authentic Cadence V -> I
Half Cadence Phrase ending on V (e.g. I –> vi –> IV –> V)
Plagal Cadence IV -> I
Deceptive Cadence V -> (any chord other than I)

Authentic cadences fall into two categories: perfect and imperfect. Perfect authentic cadences (PAC) are a root position V going to root position I. The I chord also must have the root of the chord as the top (soprano) note.

Imperfect authentic cadences (IAC) are a little varied, but can be described as VI movement without the root of the chord as the highest “voice”. They can also appear as some kind of inverted VI movement. For example: in the key of G, the chord D/F# (D major with F# in the bass) going to G is considered imperfect because the V is inverted. Likewise if the I chord is some kind of inversion as well. Lastly, if there’s any dominant substitution the cadence is imperfect. Examples would be viiI or some kind of tritone sub (don’t worry about this one for now).

Check the handy dandy image to see examples of each cadence. I’ve added roman numerals and chord names to the notation for clarity. There are of course a multitude of different cadential ideas found in music, but this is just to get you started on your journey.

The last important thing to remember at this point is context is everything. A chord just sitting by itself is not necessarily tonic. The context of a chord is what defines its function. For example, F major is the IV chord in the key of C and thus, pre-dominant. But in the key of F, it is the I chord and tonic.

Mess around with the functions of chords and try and see how some of your favorite songs fit into the scheme of things. Maybe even your own compositions! You might find that the chord progressions don’t follow any kind of tonal scheme. That might be due to a well broken rule, or maybe the song sits in the nebulous zone known as modality (which I’ll cover in a later article).

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