The course will explore the tone combinations that humans consider consonant or dissonant, the scales we use, and the emotions music elicits, all of which provide a rich set of data for exploring music and auditory aesthetics in a biological framework. Analyses of speech and musical databases are consistent with the idea that the chromatic scale (the set of tones used by humans to create music), consonance and dissonance, worldwide preferences for a few dozen scales from the billions that are possible, and the emotions elicited by music in different cultures all stem from the relative similarity of musical tonalities and the characteristics of voiced (tonal) speech. Like the phenomenology of visual perception, these aspects of auditory perception appear to have arisen from the need to contend with sensory stimuli that are inherently unable to specify their physical sources, leading to the evolution of a common strategy to deal with this fundamental challenge.
Is Music Uniquely Human?
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En provenance du cours de Duke University
Music as Biology: What We Like to Hear and Why
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Musical Scales
Why a small number of basic scales are used in music worldwide, and how a biological framework explains this and related puzzles.
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- Dale PurvesM.D.
Duke Institute for Brain Sciences
So the last lesson in the module raises another general question,
is music uniquely human?
And let me begin by showing you again the slide that I showed you earlier
on to point out that music has been around for a very long time.
You will recall perhaps that I told you that this ancient flute is
carbon dated to an age of 32,000 years and that the holes on the flute suggest
that the intervals that were being played in that ancient prehistoric era were
pretty much the same as the intervals that are being played today in a pentatonic or
diatonic, heptatonic scale that we've been talking about.
So clearly music's been around pretty much since the dawn of human history,
and that raises the question, well, okay, is that the beginning of it?
Where did it come from biologically?
How about our pre-human, pre-hominid ancestors?
Are they capable of music?
And, if not, why not?
And, if they are, in what sense are they musical?
So, Birdsong is a good example of this
debate over this issue which has gone on a long time and is still not settled.
But I think based on [COUGH] what I have been saying in the module,
there's some pretty straight-forward inferences that one can make.
So Birdsong is not, in any obvious way,
musical in the sense that it's not hitting intervals.
If you record birdsong, it's not hitting intervals of the chromatic scale,
or a diatonic or pentatonic scale.
But, it is harmonic.
So this is a spectogram of the zebra finch song here.
So here's the male zebra finch singing its song.
Here is a spectogram, a time signal of the song that plots
the ongoing song of the bird over a few seconds of time,
two and a half seconds here, against the frequency of the song.
And what you can see by these stacks in the elements,
the syllables of the bird's song, that they are harmonic.
These intervals are the harmonics in the utterance,
if you want to call it that, of the bird as it's singing its song.
And by virtue of what I said in lessons four and five, well,
okay if the bird is singing a harmonic series,
which is basically what this spectrogram is showing us.
Well, then, it should be capable of music for
the same reasons that we have been talking about with human beings.
But Birdsong is not obviously
hitting the intervals of the chromatic scale and they're many of course other
animal vocalizations that are also harmonic series.
That if you took a spectrogram of a frog or
of many other examples of animals that are communicating socially.
For purposes of mating and other biologically significant reasons,
you find harmonics in many animal vocalizations.
But they're not musical in the sense that we've been talking about.
Why is that?
Well, the answer is not known, but I think the inferences that would follow from that
are that any animal that vocalizes in a harmonic series has in principle,
the wherewithal to be musical.
And probably what's lacking is not the essence in the vocalization of musically
and the importance of recognizing that vocalization, as specific.
But the failure of sufficient socialization and the cultures that we,
over those many thousands of years and, presumably, before that ancient flute
was discovered, that human beings had music based on our recognition
of the melodies that come when we sing a song, and
particularly the music that arises when more than one individual sings it,
and the melodies are combined as intervals that define a chromatic scale,
and the scales that we use in popular music.
Bottom line is that the relative lack of music, evidence for music in
other species, including birds, it's not that they don't have the wherewithal, but
that they don't have cultural sufficient socialization to make it biologically
useful the way we have to generate music and all that follows from it.
Going back to Darwin, you remember that he was the first.
But it seems a reasonable explanation that part of the reason that we like music so
much Is it's role in courting and
love, why so many songs that are popular are about love.
I mean, if you really were to do an empirical study of popular songs today
you'd find that the vast majority are about love and
one of it's many complex aspects.
So, again other animals can be musically
adept, but they haven't developed it, presumably because they don't have
the social inclination that have made it come to life so vividly for human beings.
So let's review the main points, and there are lots of them today,
this is a pretty heavy duty lesson and let me just run through them.
First of these is that they widely use scales or
six to eight note subsets.
Five or seven interval subsets of the chromatic scale.
And that's
Puzzling because there are an enormous number of scales that are possible,
there are actually billions of scales that are possible if you think about,
just dividing the octaves in to the pitches that we can discriminate.
And only a small number of these are used and we talked about the reason why.
The argument biologically is that the similarity of
popular scales to harmonic series identifies the tone
combinations in scales that we like as vocally similar and
that's why they're appreciated and ones that are less
vocally similar are not used limiting the scales in use
over the history of music to a relatively few dozen.
Whatever number you want to put on,
it's a very small number compared to the billions that are possible.
Then we went on to say that the similarity to a harmonic series is
a possible explanation of why the scales comprise a small number of notes,
and that the degree of overlapping harmonics, can rationalize consonance,
octave similarity, we didn't really talk about that but
that's another thing that it can explain.
And that coming out of that is a natural tuning system
that's not Pythagorean, that's not just intonation.
That's not equal temperament, but
that is a natural system based on harmonic overlap.
So that's an interesting idea that I think remains to be explored and confirmed.
A corollary that I mentioned in Lesson five was that the chromatic scale and
the semi-tone are really artifacts.
They're conceptual, theoretical, didactic principals but
they're not actual scales or
units of the octave that have a physical biological basis.
And finally that given the biological basis of music
there's no reason that, in principle, other animals shouldn't have music.
But it does appear to be almost exclusively human.
Perhaps uniquely human.
Not because other animals couldn't do it, but just because they haven't evolved
the culture and the degree of socialization that
we have that makes it something that's advantageous in courting, in love or
whatever other context that the emotion that we're gonna talk about next
time makes it so important and attractive.
So just to reiterate what we're going to talk about next time.
We're going to talk about emotion in music.
Why does it have emotion and how does that play out in different cultures?
And the musical differences that are obvious in different cultural traditions.
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