A Chord Progression is a sequence of chords that achieve a larger-scale harmonic purpose than can be achieved by a single chord alone…
Such harmonic purposes include:
- Establishing a key center.
- Establishing a tonality.
- Building harmonic tension.
- Releasing harmonic tension.
- Creating a sense of forward motion and anticipation.
- Changing the mood.
- Introducing tonal ambiguity.
- Changing key center.
There are two broad classes of Chord Function:
- Chords that establish the key center and tonality (major, minor, mixolydian, dorian, blues, etc).
- Chords that create or expand harmonic motion or tension.
Here, for example, is a commonly-used chord progression in the key of C…
Listen and notice four things:
- The first C chord establishes the key center C and major-ness of the piece.
- The chords that follow create a chain of harmonic motion that leads naturally from one chord to the next.
- Each chord has a unique sound-feeling, a unique harmonic tension with respect to the key center C.
- The harmonic motion is eventually resolved with the final C chord.
This analysis is more than mere “theory”. It captures the organic essence of how humans naturally experience and enjoy music. Don’t fuss about the details right now. It is sufficient to understand that chord progressions create forward motion and typically follow logical paths based on a small number of simple formulas for creating, then resolving, harmonic tension.