Music Theory - Diatonic Chord Progressions
This lesson is intended to give a basic understanding of harmonic function related to a major key.
Harmonic Functions
At the most basic level of abstraction, each diatonic chord has one of three functions: tonic, pre-dominant, or dominant. The function of tonic chords is to establish tonality or resolve tension. Thus it is often the first and/or last chord in a song. Dominant functions to create tension that can be relieved by tonic chords. Pre-dominant chords serves to lead into dominant chords.
This gives us our first and most basic chord progression: I - IV - V - I:
fig 1 C F/C G/B C I IV V I e--0-----1------3-----0---- b--1-----1------0-----1---- g--0-----2------0-----0---- d--2-----3------0-----2---- a--3-----3------2-----3---- e--------------------------
Ok, yeah, so we already saw this in a prior lesson. Well let's switch some chords to parallels with the same harmonic function:
fig 2 Am Dm/A G/B C vi ii V I e--0-----1------3-----0---- b--1-----3------0-----1---- g--2-----2------0-----0---- d--2-----0------0-----2---- a--0-----0------2-----3---- e--------------------------
fig 3 Am F/A Em/B C vi IV iii I e--0-----1------0-----0---- b--1-----1------0-----1---- g--2-----2------0-----0---- d--2-----3------2-----2---- a--0-----0------2-----3---- e--------------------------
Those are a bit different, but they all seem to "push" in the same direction, right?
So if all these chords fall into these functions and each one leads into the next one, how do we compose? It may feel like these rules are locking us inside a cage where we can make a substitution here and there but aren't really free to branch out. Here are several points to keep in mind:
- We are only using diatonic chords.
- We are immediately moving from one function to the next, rather than hanging around and embellishing the function before moving on.
- We are confined to one key instead of modulating or borrowing from other keys.
- We haven't entertained the idea that we can ignore the functions described above.
- We are only looking at harmony, without any context of melody or rhythm. Even with all the points above, a seemingly simple progression can undertone a wide range of actual songs. Check out the "4 chord song" by Axis of Awesome.
Circle Progression
Another way to progress through chords is given to us by the circle of fifths. We haven't covered that yet, but we will soon. Essentially, it arranges notes in order of fifths, with each note being a perfect fifth higher than the previous note as we traverse the circle clockwise. Here's the notes from Cb to C# along the circle of fifths.
|------------------------------------------------| Cb - Gb - Db - Ab - Eb - Bb - F - C - G - D - A - E - B - F# - C#
Enharmonically, Gb and F# are the same pitch; so the circle is just repeating at that point, indicated by the range above the notes above.
If we use only diatonic notes for any particular major key, the 7th note does not have a diatonic perfect fifth but a diminished fifth. In C Major, B-F is a diminished fifth instead of a perfect fifth; however, we can still make the circle:
|-----------------------| F - C - G - D - A - E - B - F - C
We have already learned that the strongest harmonic resolution is from Dominant to Tonic (or V - I). The circle progression makes use of this - we simply traverse the circle counter-clockwise, using that note as the root of the next diatonic chord in the sequence. So in the key of C Major, a complete circle progression is:
C - F - Bdim - Em - Am - Dm - G - C I - IV - vii° - iii - vi - ii - V - I
We haven't talked about that Bdim chord yet, so let's leave it out. Let's also leave out the IV chord, since a IV - iii resolution may be a bit awkward. This leaves us with:
C Em Am Dm G C I iii vi ii V I e-0---0---0---1---3---0-- b-1---0---1---3---3---1-- g-0---0---2---2---0---0-- d-2---2---2---0---0---2-- a-3---2---0-------2---3-- e-----0-----------3------
Every chord leads into the next pretty seamlessly.
The circle progression gives us a basic roadmap of how to get from any chord to any other chord in the same key. Knowing harmonic function allows us to take "shortcuts" and jump some intermediate chords. For example, we know the harmonic function of IV is pre-dominant, so we can jump from IV to any dominant function chord. Let's choose V. That leaves us with I - IV ... - V - I. We're back to our basic I - IV - V - I example!