Monday, August 31, 2015

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

_This Is Your Brain on Music:  The Science of a Human Obsession_ by Daniel J. Levitin
NY:  Dutton Books, 2006
ISBN 0-525-949969-0

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

(14)  The basic elements of any sound are loudness, pitch, contour, duration (or rhythm), tempo, timbre, spatial location, and reverberation.

(24)  The lowest note on a standard piano vibrates with a frequency of 27.5 Hz.  Interestingly, this is about the same rate of motion that constitutes an important threshold in visual perception.  A sequence of still photographs - slides - displayed at or about this rate of presentation will give the illusion of motion.
NB:  24 frames per second

(29) ...every culture we know of has the octave as the basis for its music, even if it has little else in common with other musical traditions.  This phenomenon leads to the notion of circularity in pitch perception, and is similar to circularity in colors...

When men and women speak in unison, their voices are normally an octave apart, even if they try to speak the exact same pitches.  Children generally speak an octave or two higher than adults...

The octave is so basic that even some animal species  - monkeys and cats, for example - show octave equivalence, the ability to treat as similar, the way that humans do, tones separated by this amount.

(30)  Intervals are the basis of melody, much more so than the actual pitches of notes;  melody processing is relational, not absolute, meaning that we define a melody by its intervals, not the actual notes used to create them.

(34)  Every tone is 6 percent higher than the previous one, and when we increase each step by 6 percent twelve times, we end up having doubled our original frequency (the actual proportion is the twelfth root of two=1.059463...)

The particular placement of the two half steps in the sequence of the major is crucial;  it is not only what defines the major scale and distinguishes it from other scales, but it is an important ingredient in musical expectations.  Experiments have shown that young children, as well as adults, are better able to learn and memorize melodies that are drawn from scales that contain unequal distances such as this.  The presence of the two half steps, and their particular positions, orient the experienced acculturated listener to where we are in the scale.

(36)  what psychologists call declarative knowledge - the ability to talk about it [recognizing different keys]

(37)  Although it has been claimed that Indian and Arab-Persian music use "microtuning" - scales with intervals much smaller than a semitone - close analysis reveals that their scales also rely on twelve or fewer tones and the others are simply expressive variations, glissandos (continuous glides from one tone to another, and momentary passing tones, similar to  the American blues tradition of sliding into a note for emotional purposes.

(40)  So if you pluck a string and its slowest vibration frequency is one hundred times per second, the other vibration frequencies will be 2 x 100 (200 Hz), 3 x 100 (300 Hz), etc.  If you blow into a flute or recorder and cause vibrations at 310 Hz, additional vibrations will be occurring at twice, three times, four times, etc, this rate:  620 Hz, 930 Hz, 1240 Hz, etc.  When an instrument creates energy at frequencies that are integer multiples such as this, we say that the sound is harmonic, and we refer to the pattern of energy at different frequencies as the overtone series.  There is evidence that the brain responds to such harmonic sounds with synchronous neural firings - the neurons in the  auditory cortex responding to each of the components of the sound synchronize their firing rates with one another, creating a neural basis for the coherence of these sounds.

The brain is so attuned to the overtone series that if we encounter a sound that has all of the components except the fundamental, the brain fills it in for us in a phenomenon called _restoration of the missing fundamental_.

(41)  And because the electrodes put out a small electrical signal with each firing - and because the firing _rate_ is the same as a _frequency_ of firing - Petr sent the output of these electrodes to a small amplifier, and played back the sound of the owl's neurons through a loudspeaker.  What he heard was astonishing;  the melody of "The Blue Danube Waltz" sang clearly from the loudspeakers:  ba da da da da, deet deet, deet deet.  We were _hearing_ the firing rates of the neurons and they were identical to the frequency of the missing fundamental.  The overtone series had a instantiation not just in the early levels of auditory processing, but in a completely different species.

(43)  Timbre is a consequence of the overtones.  Different materials have different densities.

(50)  Timbre was what defined rock for [John R] Pierce [whom Levitin introduced to rock n roll]

(51)  The introduction of energy to an instrument - the attack phase - usually creates energy at many different frequencies that are not related to one another by simple integer multiples.  In other words, for the brief period after we strike, blow into, pluck, or otherwise cause an instrument to start making sound, the impact itself has a rather noisy quality that is not especially musical - more like the sound of a hammer hitting a piece of wood, say, than like a hammer hitting a bell or a piano string, or like the sound of wind rushing through a tube.

(52)  The third dimension of timbre - flux - refers to how the sound changes after it has started playing.  A cymbal or gong has a lot of flux - its sound changes dramatically over the time course of its sound - while a trumpet has less flux - its tone is more stable as it evolves.

(55)  At a neural level, playing an instrument requires the orchestration of regions in our primitive, reptilian brain - the cerebellum and the brain stem - as well as higher cognitive systems such as the motor cortex (in the parietal lobe) and the planning regions of our frontal lobes, the most advanced region of the brain.

Rhythm, meter, and tempo are related concepts that are often confused with one another.  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 tapes group together to form larger units.

(56)  The rhythmic ratio of 2:1, like the octave in pitch ratios, appears to be a musical universal.

(57)  The word _beat_ indicates the basic unit of measurement in a musical piece;  this is also called the _tactus_.  Most often, this is the natural point at which you would tap your foot or clap your hands or snap your fingers.

(59)  As a baseline, we considered how much variation in tempo the average person can detect;  that turns out to be 4 percent.  In other words, for a song with a tempo of 100 bpm, if the tempo varies between 96-100, most people, even professional musicians, won't detect that small change...

(63)  Whenever a note anticipates a beat - that is, when a musician plays a note a bit earlier than the strict beat would call for - this is called syncopation.  This is a very important concept that relates to expectation, and ultimately tot he emotional impact of a song.  The syncopation catches us by surprise, and adds excitement.

(65)  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."

(66)  A fundamental principle of cognitive neuroscience is that the brain provides the biological basis for any behaviors or thoughts that we experience, and so at some level there must be neural differentiation wherever there is behavioral differentiation.

(69)  A lot of people like really loud music.  Concertgoers talk about a special state of consciousness, a sense of thrills and excitement, when the music is really loud - over 115 dB.  We don't know yet why this is so.  Part of the reason may be related tot he fact that loud music saturates the auditory system, causing neorons to fire at their maximum rate.  When many, many neurons are maximally firing, this could cause an emergent property, a brain state qualitatively different form when they are firing at normal rates.  Still, some people like loud music, and some people don't.

(112)  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.

(113)  An important way that our brain deals with standard situations is that it extracts those elements that are common to multiple situations and creates a framework within which to place them;  this framework is called a schema.  The schema for the letter _a_ would be a description of its shape, and perhaps a set of memory traces that includes all the _a_'s we've ever seen, showing the variability that accompanies the schema.

(141)  This led Rosch to conclude that (a) categories are formed around prototypes;  (b) these prototypes can have a biological or physiological foundation;  (c) category membership can be thought of as a question of degree, with some tokens being "better" exemplars than others;  (d) new items are judged in relation to the prototypes, forming gradients of category membership:  and the final blow for Aristotelian theory, (e) there don't need to be any attributes which all category members have in common, and boundaries don't have to be definite.

(184)  Part of the "astonishing hypothesis" of [Francis] Crick's book was that consciousness emerges from the synchronous firing, at 40 Hz, of neurons in the brain.

(193)  Memory strength is also a function of how much we care about the experience.  Neurochemical tags associated with memories mark them for importance, and we tend to code as important things that carry with them a lot of emotion, either positive or negative.  I tell my students if they want to do well on a test, they have to really care about the material as they study it.  Caring may, in part, account for some of the early differences we see in how quickly people acquire new skills.

(202)  We also know that, on average, successful people had many more failures than unsuccessful people.  This seems counterintuitive.  How could successful people have failed more often than everyone else?  Failure is unavoidable and sometimes happens randomly.  It's what you do after the failure that is important.  Successful people have a stick-to-it-iveness.  They don't quit.

(221)  ...gray matter is that part of the brain that contains the cell bodies, axons, and dendrites, and is understood to be responsible for information processing, as opposed to white matter, which is responsible for information transmission.

(222)  Mothers (and to a lesser extent, fathers) do this quite naturally without any explicit instruction to do so, using an exaggerated intonation that the researchers call infant-directed speech or motherese.
NB:  Cross-cultural?

(239)  As Internet radio and personal music players are becoming more popular, I think that we will be seeing personalized music stations in the next few years, in which everyone can have his or her own personal radio station, controlled by computer algorithms that play us a mixture of music we already know and like and a mixture of music we don't know but we are likely to enjoy.  I think it will be important that whatever form this technology takes, listeners should have an "adventuresomeness" knob they can turn that will control the mix of old and new, or the mix of how far out the new music is from what they usually listen to.  This is something that is highly variable from person to person, and even, within one person, from one time of day to the next.

(242)  In architecture, a designer might plan for a dome to be held up by four arches.  There will necessarily be a space between the arches, not because it was planned for, but because it is a by-product of the design.  Birds evolved feathers to keep warm, but they coopted the feathers for another purpose - flying.  This is a spandrel.
NB:  Is language the spandrel of music?

(250)  Music predates agriculture in the history of our species.  We can say, conservatively, that there is no tangible evidence that language preceded music....

The best estimates are that it takes a minimum of fifty thousand years for an adaptation to show up in the human genome.  This is called evolutionary lag - the time lag between when an adaptation first appears in a small proportion of individuals and when it becomes widely distributed in the population.

(251)  One striking find is that in every society of which we're aware, music and dance are inseparable.

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