Greg is a composer and jazz trumpeter. He has a doctorate from the University of Michigan and has taught college and high school 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.
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.
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.
Another early-20th century composer, Arnold Schoenberg, wrote a famous chord in his Five Pieces For Orchestra that completely avoids consonance. Instead, he uses notes that are a step apart, but displaces one note so that the step is hidden. This weakens the dissonance so it's not quite as jarring but still gives us a tense, unstable chord. You might hear this chord as less aggressive than Stravinsky's chord; this tension might be perceived as more mysterious and veiled, since the dissonant steps are hidden from our ear.
Try to get to a piano and play these two chords - what other traits can you notice about these two approaches to dissonance?
Dissonance is a property usually ascribed to chords, or musical notes played simultaneously. Chords that are dissonant contain notes who fit together in a way that our ear finds jarring or off-putting. Traditionally, consonant (pleasant-sounding) chords derive their notes from the harmonic series, a naturally-occurring relationship between a frequency and multiples of that frequency. Notes outside the harmonic series, especially notes separated by a single step on the piano, are likely to be heard as dissonant. Some composers, such as Igor Stravinsky and Arnold Schoenberg, have used dissonance for emotional effect in their music.
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