How can an art form made from no words move us so deeply? Music, after all, carries neither language nor plain ideas; it is abstract through and through. Yet whatever it leaves unsaid it more than repays in feeling. Put on a song we love and the body quietly gives the game away, showing every sign of being emotionally stirred. Our pupils widen while heart rate and blood pressure climb; the skin's electrical resistance drops, and the cerebellum — the part of the brain we normally tie to movement — flares up in a way that seems out of place. Even the flow of blood is rerouted, drawn towards the muscles of the legs. Sound, in short, takes hold of us somewhere deep in our biology.
Much of what we now know about music's grip on us comes from a recent article in the journal Neural Frontiers, produced by a research team based in Uppsala, Sweden. For all the elaborate equipment it leaned on — functional magnetic resonance imaging (fMRI) together with positron emission tomography (PET) scanning — the design of the experiment could hardly have been plainer. From 184 people who had answered notices asking for volunteers prone to 'chills' while listening to music without words, just eight were finally kept. Each arrived with a personal playlist, the selections ranging across almost every style imaginable, techno and tango side by side; these tracks were played back while the listener's brain was watched. Running the two scanning methods at once let the team assemble a portrait of the musical brain that was strikingly exact. Their opening result was that hearing music pushes the brain's nerve cells to manufacture dopamine — a substance that does much to govern how we feel — across the dorsal as well as the ventral parts of the brain. Because both areas have been bound up with pleasure for a very long time, little here was surprising.
Far more telling was a second result. Within the caudate — a structure that helps the brain forge links between a stimulus and a response, and that fires whenever we expect money or some other kind of reward — the dopamine cells hit their peak roughly fifteen seconds ahead of each listener's best-loved moment in a piece. This interval the Uppsala team named the 'build-up phase', proposing that its role is to let us sense the approach of the part we are waiting for. But what are all these dopamine cells busy doing? Why should they burn brightest in the seconds that lead up to the musical high point rather than at the high point itself? As a rule a rush of dopamine travels hand in hand with pleasure, with a reward that has actually arrived. Here, strangely, the cells blaze most fiercely while the 'chills' are still on their way and the melody has yet to settle.
To make sense of this, it helps to turn from the neurons towards the music itself. To an outsider a piece may resemble a maze of interlocking patterns, and yet the moment that counts for most in any song or symphony is exactly the one where those patterns give way and the sound turns unpredictable. Music that stays too plain merely bores us, no more welcome than a ringing alarm clock. This squares with what many experiments have found: once a reward becomes predictable, dopamine cells soon stop reacting to it. Our excitement drains away the instant the next step is obvious. That is why a composer will sound an important note near the start, then take care to skirt that pattern through most of what follows, before at last letting it ring out again in the closing bars. And the longer the pattern we await is held back, the fiercer the release when it finally comes home.
A striking illustration of this idea comes from the musicologist Rosa Lindqvist, whose well-known study Expectation and Feeling in Music (1959) works its way through the finale of Brahms's Clarinet Quintet in B minor, Op. 115. Her purpose was to show that music lives by teasing our sense of order without ever quite surrendering to it. Over forty-four bars of the score she traces the way Brahms first lays out a clear rhythmic and harmonic figure and then, with real cunning, keeps putting off its return. In its place he offers hints and reworkings of that figure, keeping a thread of uncertainty pulled tight so that the listener's mind aches for the single resolving chord he withholds. That chord he releases only at the very close.
For Lindqvist, the feeling we hear in music rises out of just this suspense — the tension of expectations left unmet. Older accounts had dwelt on how a sound can point outward to real scenes and lived experience, a sort of 'outward' meaning; Lindqvist argued instead that musical emotion is born from the unfolding of the music on its own terms. This 'inner' meaning grows out of the very patterns a work summons up and then declines to supply. And it is that uncertainty which sets off the flood of dopamine within the caudate, as we labour to guess what is coming next. A few notes we can foresee, yet never the whole run of them, and it is this that keeps us there, listening on, waiting in hope for our reward and for the pattern to be made whole at last.
