This Is Your Brain on Music: The Science of a Human Obsession

by Daniel J. Levitin

Science is not meant to cure us of mystery, but to reinvent and reinvigorate it.

What artists and scientists have in common is the ability to live in an open-ended state of interpretation and reinterpretation of the products of our work. The work of artists and scientists is ultimately the pursuit of truth, but members of both camps understand that truth in its very nature is contextual and changeable, dependent on point of view, and that today’s truths become tomorrow’s disproven hypotheses or forgotten objets d’art.

For the artist, the goal of the painting or musical composition is not to convey literal truth, but an aspect of a universal truth that if successful, will continue to move and to touch people even as contexts, societies, and cultures change.

Music listening, performance, and composition engage nearly every area of the brain that we have so far identified, and involve nearly every neural subsystem.

Music theorists have an arcane, rarified set of terms and rules that are as obscure as some of the most esoteric domains of mathematics.

Norm doesn’t have any knowledge about music in the technical sense—he can tell me that he likes a certain song, but he can’t tell me what the names of the chords are. He is, however, an expert in knowing what he likes. This is not at all unusual, of course. Many of us have a practical knowledge of things we like, and can communicate our preferences without possessing the technical knowledge of the true expert.

Like science, music over the years has proved to be an adventure, never experienced exactly the same way twice.

As the composer Edgard Varèse famously defined it, “Music is organized sound.”

The basic elements of any sound are loudness, pitch, contour, duration (or rhythm), tempo, timbre, spatial location, and reverberation. Our brains organize these fundamental perceptual attributes into higher-level concepts—just as a painter arranges lines into forms—and these include meter, harmony, and melody. When we listen to music, we are actually perceiving multiple attributes or “dimensions.”

Pitch is a purely psychological construct, related both to the actual frequency of a particular tone and to its relative position in the musical scale. It provides the answer to the question “What note is that?” (“It’s a C-sharp.”)

The two terms, tone and note refer to the same entity in the abstract, but we reserve the word tone for what you hear, and the word note for what you see written on a musical score.)

Rhythm refers to the durations of a series of notes, and to the way that they group together into units.

Tempo refers to the overall speed or pace of the piece. If you were tapping your foot, dancing, or marching to the piece, it’s how fast or slow these regular movements would be.

Contour describes the overall shape of a melody, taking into account only the pattern of “up” and “down” (whether a note goes up or down, not the amount by which it goes up or down).

Timbre (rhymes with amber) distinguishes one instrument from another—say, trumpet from piano—when both are playing the same written note. It is a kind of tonal color that is produced in part by overtones...

amplitude of a tone.

Reverberation refers to the perception of how distant the source is from us in combination with how large a room or hall the music is in; often referred to as “echo” by laypeople, it is the quality that distinguishes the spaciousness of singing in a large concert hall from the sound of singing in your shower.

Miles Davis famously described his improvisational technique as parallel to the way that Picasso described his use of a canvas: The most critical aspect of the work, both artists said, was not the objects themselves, but the space between objects.

In Miles’s case, he described the most important part of his solos as the empty space between notes, the “air” that he placed between one note and the next. Knowing precisely when to hit the next note, and allowing the listener time to anticipate it, is a hallmark of Davis’s genius. This is particularly apparent in his album Kind of Blue.

(The

official definition of the Acoustical Society of America is that timbre is everything about a sound that is not loudness or pitch.

If a string is vibrating so that it moves back and forth sixty times in one second, we say that it has a frequency of sixty cycles per second. The unit of measurement, cycles per second, is often called Hertz (abbreviated Hz) after Heinrich Hertz, the German theoretical physicist who was the first to transmit radio waves (a dyed-in-the-wool theoretician, when asked what practical use radio waves might have, he reportedly shrugged, “None”). If you were to try to mimic the sound of a fire engine siren, your voice would sweep through different pitches, or frequencies (as the tension in your vocal folds changes), some “low” and some “high.”

Pressing a piano key causes a hammer to strike one or more strings inside the piano. Striking a string displaces it, stretching it a bit, and its inherent resiliency causes it to return toward its original position.

Sound waves impinge on the eardrums and pinnae (the fleshy parts of your ear), setting off a chain of mechanical and neurochemical events, the end product of which is an internal mental image we call pitch. If a tree falls in a forest and no one is there to hear it, does it make a sound? (The question was first posed by the Irish philosopher George Berkeley.) Simply, no—sound is a mental image created by the brain in response to vibrating molecules.

Similarly, in Peter and the Wolf, Prokofiev uses the flute to represent the bird, and the French horn to indicate the wolf. The characters’ individuality in Peter and the Wolf is expressed in the timbres of different instruments and each has a leitmotiv—an associated melodic phrase or figure that accompanies the reappearance of an idea, person, or situation.

The auditory cortex also has a tonotopic map, with low to high tones stretched out across the cortical surface. In this sense, the brain also contains a “map” of different pitches, and different areas of the brain respond to different pitches. Pitch is so important that the brain represents it directly; unlike almost any other musical attribute, we could place electrodes in the brain and be able to determine what pitches were being played to a person just by looking at the brain activity.

This difference is timbre, and it is the most important and ecologically relevant feature of auditory events. The timbre of a sound is the principal feature that distinguishes the growl of a lion from the purr of a cat, the crack of thunder from the crash of ocean waves, the voice of a friend from that of a bill collector one is trying to dodge.

Briefly, rhythm refers to the lengths of notes, tempo refers to the pace of a piece of music (the rate at which you would tap your foot to it), and meter refers to when you tap your foot hard versus light, and how these hard and light taps group together to form larger units.

In “Back in Black,” the drummer plays his cymbal twice for every beat (eighth notes) and the bass player plays a simple, syncopated rhythm perfectly in time with the guitar. On “Straight Up” there is so much going on, it is difficult to describe it in words.

Normally, there would be a word on every downbeat, as in children’s nursery rhymes. But in lines two and four of the song, the downbeat comes and he’s silent! This is another way that composers build excitement, by not giving us what we would normally expect.

When people clap their hands or snap their fingers with music, they sometimes quite naturally, and without training, keep time differently than they would do with their feet: They clap or snap not on the downbeat, but on the second beat and the fourth beat. This is the so-called backbeat that Chuck Berry sings about in his song “Rock and Roll Music.”

Sometimes critics talk about the dynamic range that is achieved on a high-quality music recording; if a record has a dynamic range of 90 dB, it means that the difference between the softest parts on the record and the loudest parts is 90 dB—considered high fidelity by most experts, and beyond the capability of most home audio systems.

Some grouping factors are intrinsic to the objects themselves—shape, color, symmetry, contrast, and principles that address the continuity of lines and edges of the object.

body. To most of us, it certainly feels as though our minds are something unique and distinctive, separate from just a bunch of neurochemical processes. We have a feeling of what it is like to be me, what it is like to be me reading a book, and what it is like to think about what it is like to be me. How can me be reduced so unceremoniously to axons, dendrites, and ion channels? It feels like we are something more. But this feeling could be an illusion,

The average brain consists of one hundred billion (100,000,000,000) neurons. Suppose each neuron was one dollar, and you stood on a street corner trying to give dollars away to people as they passed by, as fast as you could hand them out—let’s say one dollar per second. If you did this twenty-four hours a day, 365 days a year, without stopping, and if you had started on the day that Jesus was born, you would by the present day only have gone through about two thirds of your money. Even if you gave away hundred-dollar bills once a second, it would take you thirty-two years to pass them all out.

Each neuron is connected to other neurons—usually one thousand to ten thousand others. Just four neurons can be connected in sixty-three ways, or not at all, for a total of sixty-four possibilities. As the number of neurons increases, the number of possible connections grows exponentially (the formula for the way that n neurons can be connected to each other is 2(n*(n-1)/2)): For 2 neurons there are 2 possibilities for how they can be connected For 3 neurons there are 8 possibilities For 4 neurons there are 64 possibilities For 5 neurons there are 1,024 possibilities For 6 neurons there are 32,768 possibilities

Similarly, you can see how it is that all the songs we have ever heard—and all those that will ever be created—could be made up of just twelve musical notes (ignoring octaves). Each note can go to another note, or to itself, or to a rest, and this yields twelve possibilities. But each of those possibilities yields twelve more. When you factor in rhythm—each note can take on one of many different note lengths—the number of possibilities grows very, very rapidly.

Brains, on the other hand, can work on many things at once, overlapping and in parallel. Our auditory system processes sound in this way—it doesn’t have to wait to find out what the pitch of a sound is to know where it is coming from; the neural circuits devoted to these two operations are trying to come up with answers at the same time.

Music, then, can be thought of as a type of perceptual illusion in which our brain imposes structure and order on a sequence of sounds. Just how this structure leads us to experience emotional reactions is part of the mystery of music. After all, we don’t get all weepy eyed when we experience other kinds of structure in our lives, such as a balanced checkbook or the orderly arrangement of first-aid products in a drugstore (well, at least most of us don’t). What is it about the particular kind of order we find in music that moves us so? The structure of scales and chords has something to do with it, as does the structure of our brains. Feature detectors in our brains work to extract information from the stream of sounds that hits our ears. The brain’s computational system combines these into a coherent whole, based in part on what it thinks it ought to be hearing, and in part based on expectations. Just where those expectations come from is one of the keys to understanding how music moves us, when it moves us, and why some music only makes us want to reach for the off button on our radios or CD players. The topic of musical expectations is perhaps the area in the cognitive neuroscience of music that most harmoniously unites music theory and neural theory, musicians and scientists, and to understand it completely, we have to study how particular patterns of music give rise to particular patterns of neural activations in the brain.

Similarly, we have learned that certain sequences of tones go together, and we expect them to continue to do so. We expect certain pitches, rhythms, timbres, and so on to co-occur based on a statistical analysis our brain has performed of how often they have gone together in the past. We have to reject the intuitively appealing idea that the brain is storing an accurate and strictly isomorphic representation of the world. To some degree, it is storing perceptual distortions, illusions, and extracting relationships among elements. It is computing a reality for us, one that is rich in complexity and beauty. A basic piece of evidence for such a view is the simple fact that light waves in the world vary along one dimension—wavelength—and yet our perceptual system treats color as two dimensional (the color circle described on page 29). Similarly with pitch: From a one-dimensional continuum of molecules vibrating at different speeds, our brains construct a rich, multidimensional pitch space with three, four, or even five dimensions (according to some models). If our brain is adding this many dimensions to what is out there in the world, this can help explain the deep reactions we have to sounds that are properly constructed and skillfully combined.

If we acknowledge that the brain is constructing a version of reality, we must reject that the brain has an accurate and strictly isomorphic representation of the world.

People who work with image files all the time are able to look at the stream of 0s and 1s and tell something about the nature of the photograph—not at the level of whether it is a human or a horse, perhaps, but things like how much red or gray is in the picture, how sharp the edges are, and so forth.

Of course, the computer (brain) is running a lot of fancy software (mind) that translates the code effortlessly. Most of us don’t have to concern ourselves with the code itself at all. We scan a photo or rip a song to our hard drive, and when we want to see it or hear it, we double-click on it and there it appears, in all its original glory. This is an illusion made possible by the many layers of translation and amalgamation going on, all of it invisible to us. This is what the neural code is like.

Low notes create wide grooves, high notes create narrow grooves, and a needle dropped inside the grooves is moving thousands of times per second to capture the landscape of the inner wall. If a person knew many pieces of music well, it would be possible to characterize them in terms of how many low notes there were (rap music has a lot, baroque concertos don’t), how steady versus percussive the low notes are (think of a jazz-swing tune with walking bass as opposed to a funk tune with slapping bass), and to learn how these shapes are encoded in vinyl. This fellow’s skills are extraordinary, but they’re not inexplicable.

Neurotransmitters are chemicals that travel throughout the brain and bind to receptors attached to other neurons. Receptors and neurotransmitters can be thought of as locks and keys respectively. After a neuron fires, a neurotransmitter swims across that synapse to a nearby neuron, and when it finds the lock and binds with it, that new neuron starts to fire.

Speech processing is primarily left-hemisphere localized, although certain global aspects of spoken language, such as intonation, emphasis, and the pitch pattern, are more often disrupted following right-hemisphere damage.

The ability to distinguish a question from a statement, or sarcasm from sincerity, often rests on these right-hemisphere lateralized, nonlinguistic cues, known collectively as prosody. It is natural to wonder whether music shows the opposite asymmetry, with processing located primarily on the right. There are many cases of individuals with brain damage to the left hemisphere who lost the power of speech, but retained their musical function, and vice versa. Cases like these suggest that music and speech, although they may share some neural circuits, cannot use completely overlapping neural structures.

There is also new evidence that tracking the ongoing development of a musical theme—thinking about key and scales and whether a piece of music makes sense or not—is lateralized to the left frontal lobes.

The most important way that music differs from visual art is that it is manifested over time. As tones unfold sequentially, they lead us—our brains and our minds—to make predictions about what will come next.

The structural processing—musical syntax—has been localized to the frontal lobes of both hemispheres in areas adjacent to and overlapping with those regions that process speech syntax, such as Broca’s area, and shows up regardless of whether listeners have musical training.