If piano teaching were really as traditional as many contemporary teachers imagine, then, like keyboard students in the 18th and 19th centuries, today’s students would more often be required to learn basic creative tasks like harmonizing a melody. Being able to harmonize a melody is a useful and satisfying skill for every musician, and opens up new vistas for understanding music theory and its creative applications. Many students noodle at the keyboard and create a melody they like, but are at a loss for how to flesh it out with chords.
The easiest way to learn how to harmonize a melody is to limit the chords to the basic diatonic triads. The diatonic triads are three-note chords built on each note of a diatonic scale. The diatonic triads in the key of C major are:
Not sure what these chords and their accompanying symbols are? Learn about the 10 Fundamental Chords.
Harmonic Function
The first step in learning how to harmonize a melody is to understand the function (purpose) of various chords. Since chords are the essence of harmony, we call this harmonic function. Specifically, harmonic function concerns the relationship of a chord to its tonal center (the tonic or home note of the key). This relationship involves the tendency of a chord to either rest or push the music forward, based on the chord’s degree of stability.
The three harmonic functions are tonic, subdominant and dominant. While the I, IV and V chords are the primary tonic, subdominant and dominant chords respectively, for the purposes of understanding harmonic function the other diatonic chords (II, III, VI and VII) also fall into one of these three categories.
The Tonic Chords (I, III, VI)
Function: temporary or permanent rest
The tonic chords are the most stable of the seven diatonic triads. For example, the authentic and plagal cadences both resolve to a tonic chord (I).
The primary tonic chord is the I chord. The alternate tonic chords are III and VI.
The Subdominant Chords (IV, II)
Function: contrast with tonic; set up dominant
The subdominant chords are less stable than the tonic chords. They are used to contrast with tonic chords or set up dominant chords. They have a moderate tendency to resolve to another chord.
In common practice (classical) music, the primary subdominant chord is the IV chord and the alternate subdominant chord is II. However, in contemporary music II is used as or more often than IV.
The Dominant Chords (V, VII)
Function: build desire for resolution
The dominant chords are the least stable chords. This instability propels the music forward and typically builds an expectation of resolution. They have a strong tendency to resolve to another chord, typically (though not always) a tonic chord.
The primary dominant chord is the V chord. The alternate dominant chord is VII, which is used in common practice music but rarely found in contemporary popular music. The V7 tetrad is employed more often than the V triad, even when all the other chords are triads. The V7 tetrad is more unstable and creates a more intense expectation of resolution (and satisfaction upon that resolution) than the V triad. Play the following two progressions (both authentic cadences) to hear the difference:
To summarize, the functions of the seven diatonic triads (and V7) are:
Exercise
Now it’s time for some practice. In the three excerpts below label each chord with the correct Roman numeral followed by its harmonic function in parentheses. See example below the first chord.
Then play each melody with the chords, listening for the relationship of each chord’s function to the melodic phrases (i.e., tonic for rest, subdominant for movement, dominant for strong expectation of resolution).
Understanding harmonic function is the foundation for learning to harmonize melodies, which is essential for composing effective songs or piano pieces. Want to learn more? Try virtual lessons with me via Skype or Facetime.