# Consonance and dissonance

*Module 4 · Lesson 7: Intervals · BazzLow*

> Describe intervals as stable or tense and know the usual classification.

Before this lesson: [4.4 Augmented, diminished and the tritone](https://bazzlow.com/en/intervals/augmented-diminished-tritone/)

Some intervals sound calm and finished, others sound tense. This lesson names that difference, because bass lines and chords use it constantly.

## Stable and tense

**Consonant** intervals sound stable, at rest. **Dissonant** intervals sound tense and seem to want to move; that movement is called **resolution**. Dissonance is not “bad”: music moves by building tension and releasing it. Later lessons use this idea for chords (Module 8) and bass lines (Module 9).

## The usual classification

*The usual classification of intervals in Western music.*

| Group | Intervals | Examples from C |
| --- | --- | --- |
| Perfect consonances | unison, octave, perfect 5th; the perfect 4th usually counts here too, but is treated as a dissonance in some classical part-writing contexts | C–C, C–G |
| Imperfect consonances | major and minor 3rds, major and minor 6ths | C–E, C–A♭ |
| Dissonances | major and minor 2nds, major and minor 7ths, the tritone | C–D, C–B, C–F♯ |

## A hint from the numbers

The simplest frequency ratios sound the most consonant: the octave is 2:1, the fifth 3:2, the fourth 4:3, the major third 5:4 and the minor third 6:5. Equal temperament (lesson 1.4) slightly alters all of them except the octave.

## Try it

Play a root and its perfect 5th together: open E and B at fret 2 on the A string. Then a root and its minor 2nd: A at fret 5 on the E string and B♭ at fret 1 on the A string. Describe the difference in your own words.

## New terms

- consonance
- dissonance
- resolution
- perfect consonance
- imperfect consonance

Page: https://bazzlow.com/en/intervals/consonance-and-dissonance/