Harmony
Consonance and dissonance
Consonance describes intervals and chords heard as stable and restful; dissonance describes those that create tension and ask for resolution, like the tritone in G7 moving to C.
What are consonance and dissonance?
A consonance sounds stable: you could end the song on it. A dissonance creates tension, a sense that something has to move. It is not about nice versus wrong: music moves forward precisely by alternating tension and release.
Perception also depends on style and era. A major seventh (C against B in Cmaj7) was a strict dissonance in classical harmony; in bossa nova or pop, Cmaj7 sounds soft and completely settled.
Which intervals are consonant and which are dissonant?
The traditional ranking of intervals, measured from C:
| Interval | Example | Category |
|---|---|---|
| Unison, octave | C-C | perfect consonance |
| Perfect fifth | C-G | perfect consonance |
| Perfect fourth | C-F | consonant or dissonant depending on context |
| Thirds, sixths | C-E, C-Eb, C-A, C-Ab | imperfect consonances |
| Seconds, sevenths | C-D, C-Db, C-B, C-Bb | dissonances |
| Tritone | C-F# | dissonance |
Minor seconds and major sevenths are the harshest; major seconds and minor sevenths are milder.
How can you hear the difference on guitar?
Play these pairs together and let them ring:
- Fifth: open low E string + A string, 2nd fret (E and B). That is an E5 power chord, solid and full.
- Major third: open G and B strings (G and B). Sweet and singing.
- Minor second: B string, 6th fret (F) + open high E (E). A clear rub, almost a wobble.
- Tritone: G string, 4th fret (B) + B string, 6th fret (F). Restless.
Now move the tritone to G string, 5th fret (C) + B string, 5th fret (E): B rises, F falls, and the tension resolves. That is the heart of the G7 to C cadence.
How do chords use dissonance?
Suspended chords show tension and release clearly. Play Dsus4 (x-x-0-2-3-3), then D (x-x-0-2-3-2): the G on the high E string falls to F# and the chord settles.
Extended chords use dissonance as colour without resolving it: Cadd9 (x-3-2-0-3-0) puts D against C and E, Cmaj7 (x-3-2-0-0-0) puts B against C. To see how one added note changes a chord's name, place it on the virtual neck of the chord identifier.
Key takeaways
- Consonance means stability; dissonance means tension that asks for movement.
- Octaves, fifths, thirds and sixths are consonant; seconds, sevenths and the tritone are dissonant.
- A dissonance usually resolves by a half step or whole step.
- In pop and jazz, mild dissonances (9ths, maj7) are also used purely as colour.
Frequently asked questions
Why is the perfect fourth sometimes called dissonant?
Between two upper voices, a fourth sounds open and stable. But when it is formed against the bass, as in a sus4 chord or a second-inversion triad, it wants to fall to the third. Classical harmony therefore treats it as a dissonance above the bass.
Is the tritone really the devil in music?
The nickname diabolus in musica comes from theorists who found it hard to sing and unstable. Today the tritone is everywhere: it defines every dominant seventh chord (B and F in G7) and colours the blues through the flat fifth of the blues scale.
How do you use dissonant notes in a solo?
Put them on weak beats and resolve them to a chord tone on the next beat. Over a C chord, play F on the offbeat and then E on the beat: the dissonance becomes expressive instead of sounding like a mistake.
Related terms
Practise in the workshop
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