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

C Em Am Dm G C