Why it's great to be deceived

Here's my third column for the Italian science magazine Sapere on music cognition. It mentions one of my favourite spine-tingling moments in music.

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In my last column I explained that much of the emotional power of music seems to come from violations of expectation. We think the music will do one thing, but it does another. Or perhaps it just delays what we were expecting. We experience the surprise as an inner tension. You might think this would make music hard to listen to, rather than pleasurable. And indeed it’s a delicate game: if our expectations are foiled too often, we will just get confused and frustrated. Contemporary classical music has that effect on many people, although I’ll explain another time why this needn’t mean such music is bad or unlistenable. But if music always does what we expect, it becomes boring, like a nursery rhyme. Children need nursery rhymes to develop their expectations, but eventually they are ready for something more challenging.

A lot of music does meet our expectations for much of the time: it stays in key and in rhythm, and there is lots of repetition (verse-chorus-verse…). But the violations add spice. One way they can do this is to deliver notes or chords other than the ones we anticipate. Western audiences become very accustomed to hearing sequences of chords called cadences, which round off a musical phrase. If Bach or Mozart wrote a piece in, say, C major, you could be sure it would end with a C major chord (the so-called tonic chord): that just seems the “right” place to finish. Usually this final chord is preceded by the so-called “dominant” chord rooted on the fifth note of the scale (here G major). The dominant chord sets us up to expect the closing tonic chord. This pairing is called an authentic or perfect cadence.

Imagine the surprise, then, when you think you’re being given an authentic cadence but you get something else. That’s what happens about two-thirds of the way through Bach’s Prelude in E flat Minor from the first book of The Well Tempered Clavier, one of the most exquisite pieces Bach ever wrote. Here the prelude seems about to end [at 2:56 in the Richter recording here]: there’s an E flat minor chord (the tonic) followed by a dominant chord (B flat), and we think the next chord will be the closing tonic. But it isn’t. Never mind the fancy name of the chord Bach uses – it very definitely doesn’t close the phrase, but leaves it hanging. The effect is gorgeously poignant. This is sometimes known as a deceptive cadence: the musical term already reflects the idea that our expectations are being deceived. The tonic E flat minor does arrive moments later, and then we sigh as we finally get our delayed resolution.

Electrical brain-scanning studies show that we experience this kind of musical deception the same way as we experience a violation of grammatical syntax – such as when a sentence ends this like. There’s an electrical signal in the brain that signifies our “Huh?” response. This is just one of the ways in which the brain seems to process music and language using the same neural circuits – one way music literally ‘speaks’ to us.