Why does musical harmony sound good?

📓 The short answer

Musical harmony that sounds good is called consonant harmony. We prefer consonant harmony because it is mathematically balanced, culturally ingrained, and easier for our brains to process.

📚 The long answer

There are two types of musical harmony: consonant and dissonant harmonies. The difference essentially it boils down to what sounds like a singular tone (even though it's a combination of tones) and what sounds like multiple tones played randomly together.

🔊Not sure what I mean? Here are some examples:

• ​Consonant harmony​
• ​Dissonant harmony​

There are three main reasons why consonant musical harmony sounds good to us:

1. Consonance: We like things that are mathematically balanced

Harmony is just math. You've probably heard of an octave which has a ratio of 2:1 (one note placed twice as high as the other). When those two tones are played together, they sound pleasing and almost like one singular tone. The chart above is an example of a 2:1 tone ratio, as the top wave completes 2 cycles for every 1 cycle the bottom wave does. Other pleasing harmonies like the "perfect fifth" follow a nice, round ratio (3:2).

There is symmetry and balance with the overlap of these notes – and we like that. As scientist Alan Lightman puts it, "Symmetry represents order, and we crave order in this strange universe we find ourselves in... [It] helps us make sense of the world around us".
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Dissonance is the opposite. When notes are played together that do not have balanced ratios, the sound waves clash and interfere with one another. This results in a phenomenon called "beating," which isn't particularly pleasing. Watch the video I made of two tones (440 Hz and 441 Hz) to hear what beating sounds like.​

2. Familiarity: We like things that we've heard before

There's also a familiarity to consonant harmonies that acts as a feedback loop:

While there are definitely different cultural preferences for harmonies, consonant ones are widely loved and used in different types of music. Musicians often use consonant harmonies to elicit feelings of joy, celebration, triumph, and safety. Dissonant harmonies are used to create feelings of unease, fear, and discomfort (so they aren't as frequently used).

3. Neurological rewards: Our brain likes harmony

Our love of consonant harmonies isn't a conscious preference – our brains are wired to like them. Because of the balanced sound wave ratios of consonance, it's easier for our brains to process them for us to hear. Comparatively, dissonance comes in as multiple, erratic waves that are challenging to process.

We're simply born to hear the contrast and prefer consonance. Fun fact: Even babies and monkeys and identify the difference between consonant and dissonant harmonies.
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​Sources​

📖 Book of the week

​You Are the Music: How Music Reveals What It Means to Be Human by Victoria Williamson​

This captivating book takes you on a journey that begins in the womb, exploring how music shapes our development even before we're born. From there, it delves into the ways music influences our emotional well-being, memory, and social connections as we grow into adulthood. Williamson skillfully weaves together scientific insights and personal anecdotes, providing a comprehensive understanding of the profound role that music plays in our lives at every stage. It's a fascinating exploration that will leave you with a deeper appreciation for the power of music in shaping our human experience.

👀 Catch up on other curious questions

• ​Why do (some) sunsets turn the sky pink?​
• ​What is quantum entanglement?​
• ​Why does electricity make a humming noise?​​

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