Chords and melody
Understand how chords are chosen under a melody and what that means for the bass.
Behind every chord chart is a melody that someone harmonized. Understanding how that works tells you why the chords are what they are, and how a bass line can relate to the tune.
Harmonizing
Choosing chords for a melody is harmonizing. A melody note is usually a chord tone of the chord under it, at least on strong beats. Every scale note belongs to three diatonic chords (lesson 8.1), so the same melody can be harmonized in different ways. Chord charts of one song often differ, and each version can be correct.
| Note | As root | As 3rd | As 5th |
|---|---|---|---|
| C | C | Am | F |
| D | Dm | B° | G |
| E | Em | C | Am |
| F | F | Dm | B° |
| G | G | Em | C |
| A | Am | F | Dm |
| B | B° | G | Em |
Choices are guided by function (lesson 8.4) and by mood: a minor chord under a note darkens the sound. Chords usually change on strong beats (beat 1, and often beat 3 in 4/4), not under every melody note. Melody notes that are not in the chord, such as passing notes, work the same way as in bass lines (lesson 9.4).
Here is a short original melody in C, written in the bass clef range, with two harmonizations and their root bass lines. The strong-beat notes are chord tones in both.
The outer voices
The bass and the melody are the outer voices of the music. Ways the bass can move relative to the melody:
- contrary motion: opposite directions; the most independent;
- oblique motion: one moves, one stays;
- similar motion: same direction;
- parallel motion: same direction, same interval.
A good bass line mixes them and does not just double the melody.
Sing or play a short phrase you know in C. For each strong-beat note, list the three chords that contain it and choose one. Play the roots.