Dissonant: Definition, Music, Harmony & Chords

Instructor: Greg Simon

Greg is a composer and jazz trumpeter. He has a doctorate from the University of Michigan and has taught college and high school music.

This lesson will introduce you to the musical concept of dissonance. You'll learn about what makes us hear dissonance, as well as its opposite, consonance. We'll also look at how composers have used dissonance in their music.

Music That Hurts

Have you ever noticed how some music feels good to listen to? Put on a piano piece by Beethoven or Mozart - your ear finds most of what it's hearing comfortable, right? What you're hearing is a musical principal at work called consonance: musical materials that, when played together, complement one another in a way our ear finds comfortable.

But not all music is quite so well-fitting. Go to a piano and strike an adjacent black and white key -- yeowch! Your ear twitches in discomfort at the clashing sound of it. That's dissonance: the clash between two notes that can be so striking, it hurts. This article will dive deeper into the concept of dissonance, show you why it's so uncomfortable and give you some examples of how composers use it for emotional effect.

The Harmonic Series

Most of how we perceive consonance and dissonance comes from a natural phenomenon called the harmonic series. All notes are actually sound vibrations at specific frequencies, or speeds of vibration. The harmonic series is a relationship between different vibrating frequencies. Simply put, a note that vibrates at frequency x will also activate vibrations at frequencies that are multiples of x. The diagram shown here lists the notes of the harmonic series activated by a low C; you might notice that the notes shown are all either C, E, or G.

The harmonic series on C
The harmonic series on C. Image by Greg Simon.

Consonance or dissonance is most visible when notes are played simultaneously, creating a chord. Chords created using the notes C, E, and G will sound consonant in virtually any combination because their frequencies are related -- if you have a piano handy, go try it out! You can construct a similar chord using any other trio of tones; as long as the notes are related by harmonic series, the result will be consonant.

Also note that the tones of the harmonic series are separated from one another -- that is, none of the notes pictured are adjacent to each other on the piano. Notes separated from each other by a step, or notes that are next to each other on a keyboard, will be especially dissonant with each other. B and C are pictured here, but as with notes related via the harmonic series, you will find dissonance between any two notes related by a step.

A musical step
A musical step between B and C. Image by Greg Simon.

Composing Dissonance

So how have composers used dissonance to affect their listeners? Dissonance can be a powerful tool to make an audience member feel tension or discomfort, or to express emotions that are more complex than the comfort that consonance makes us feel. Different composers have come up with different methods for creating dissonant chords.

Igor Stravinsky, in his landmark composition The Rite of Spring, composed a chord built of a major triad and a seventh chord (two consonant structures) superimposed on one another. These two chords clash with one another, and the strong dissonance cancels out the consonance. Listening to this chord, you might feel a sense of conflict and tension, even aggressiveness as the consonant forces battle against each other.

Stravinsky, The Rite of Spring
From The Rite of Spring by Igor Stravinsky. Image by Greg Simon.

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