Harmony is the most advanced building block. It is the pitches above and below the melody, grouped together into chords. You might imagine melody as the horizontal sounds and harmony as the vertical sounds of your song. The notes in a chord are either literally stacked in a three-note triad — though sometimes a two-note “power chord” (fifth chord) or four-note seventh chord — or played one right after another in sequence (arpeggio).
Depending on the intervals in its component notes — and the consonance or dissonance among them — each chord will evoke a different feeling. For example, listen to “Jingle Bells” played with minor chords instead of major chords. In simple terms, major chords express happiness, and minor chords express sadness.
In addition to the emotion within a chord, its notes will also evoke a feeling based on their relationship with the melody’s home base, on their consonance or dissonance with the song’s tonic (key). The third, fifth, and sixth notes above the tonic are consonant, and the most consonant chord is the major chord, built with the tonic pitch plus the third and fifth pitches above it. For example, a C chord includes C (root), E (third), and G (fifth) pitches.
Dissonant chords, that is, chords with tension, include pitches that clash with the tonic. The second, fourth, and seventh notes from the tonic increase tension, and the most common dissonant chord is the seventh chord. For example, a C7 chord includes C (root), E (third), G (fifth), and B-flat (seventh) pitches.
Good harmony, like good melody, balances the tense and relaxed moments. “The creation and destruction of … tensions is essential,” composer Frank Zappa said. “Consistent and ‘regular’ throughout is, for me, equivalent to watching a movie with only ‘good guys’ in it — or eating cottage cheese.”
Chord changes (progressions) often happen on downbeats. The most common progression features I-IV-V, or chords built from the first, fourth, and fifth pitches in the song’s tonic scale. For example, a progression from C (I) to F (IV) to G (V) chords. These can appear in any order, e.g., I-V-IV, IV-I-V. One visual reminder of those relationships is the Circle of Fifths. If you read the diagram clockwise, the chord pattern is IV-I-V, that is, subdominant (IV), tonic (I), and dominant (V).
Examples of songs that contain I-IV-V progressions include “All I Want for Christmas Is You” (1994) by Mariah Carey (I-IV-V), “Mama, I’m a Big Girl Now” (2002) by Shaiman and Wittman from Hairspray (I-IV-V), “Let It Go” (2013) by Robert and Kristen Lopez from Frozen (I-V-IV), “Hello” (2015) by Adele (I-V-IV), and “Despacito” (2017) by Luis Fonsi (IV-I-V).
You can include nearly any type of chord in between I-IV-V, for differing degrees of tension and relaxation, but the clue we have reached the end of a song (or the end of a stanza) is a cadence, a progression that moves back to the tonic key. The most common are those moving V-I (authentic cadence) and IV-I (amen cadence).
For more on chords, check out Music Theory Academy’s chords lesson series.
Next, the accompaniment.