# Chords and melody

*Module 9 · Lesson 6: Building bass lines · BazzLow*

> Understand how chords are chosen under a melody and what that means for the bass.

Before this lesson: [9.3 Chord tones over changes](https://bazzlow.com/en/building-bass-lines/chord-tones-over-changes/) · [8.1 Diatonic triads](https://bazzlow.com/en/harmony-in-a-key/diatonic-triads/)

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.

*The three diatonic chords that contain each note of C major.*

| 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.

> **Diagram:** An original four-bar melody in C: E G E D | C D E | G A G E | D E C.

> **Diagram:** Harmonization 1, with the root bass line: C | C | Em | G then C.

> **Diagram:** Harmonization 2, with the root bass line: Am | Am | C | G then C. Same melody, different colour.

## 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.

## Try it

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.

## New terms

- harmonizing
- outer voices
- contrary motion
- oblique motion
- similar motion
- parallel motion

Page: https://bazzlow.com/en/building-bass-lines/chords-and-melody/