Perception of Music

Neuroscientist Diana Omigie on tuning systems in different cultures, congenital amusia and aspects that influence how we perceive music

videos | March 14, 2019

With a topic as broad as music perception it’s quite difficult to know where to start, so I thought I’d start with a scenario. So imagine that you are in a foyer of a concert hall and perhaps you’ve been dragged there by a parent, maybe you’re just a kid, or perhaps you’re the parent who’s done the dragging, or perhaps you’re just there with a peer, a friend, and you’re both super excited to be there. So what happens is that the ushers are telling you to come into the auditorium, so you’re going into the auditorium, you take your place and at some point you begin to read your program notes and it tells you what you have to expect, that there are going to be the compositions from Bach, straight to a modern composer straight through to the modernist composer Webern. That’s all very interesting and exciting. At some point your attention is drawn to the stage and there you see that the concert master has invited the oboe to play a note and the oboe’s note has been followed by the woodwinds and then the brass, the rest of the brass instruments. And before you know it slowly but surely all the instruments are playing the same note: it’s 440 Hertz, it’s what we call A in the western tone system. And then the conductor comes in to a round of applause and then a general hush as you wait for the music to start.

So I started with this scenario because I thought it highlights that quite early on already just how many things can influence how we perceive music. Take for instance the fact that you are in an auditorium, so it’s a live performance. You aren’t just listening to the music, you’re also watching it being performed, and we know that actually this could have a huge influence on how we hear or perceive the music. Another thing to consider is that you’ve been reading about the music you’re about to hear, you know, who it was composed by, perhaps you’ve also been told what to listen out for while you’re listening. So again you have this top-down information which we know from research can really influence how you perceive the bottom-up information which is coming in into your ears.

But I’d like to start by sort of focusing on something that’s even more fundamental than what’s coming in through your eyes and what you’ve read about the music and you’re about to hear and talk about why the performers actually chose to go through the whole process of tuning their instruments. You might say: well, it’s just so that they are to play in tune, but this reminds us actually that there’s a huge organizing principle in music which is that we use very specific frequencies out of all the possible frequencies we can use and that’s brings us the notion of a tuning system.

A tuning system is basically a system that defines how we should select specific frequencies out of all the possible frequencies we could use. In different cultures we have different tuning systems, most of them revolve around this notion of octave equivalence and that’s just generally the notion that the two pitches are an octave apart if they have a frequency ratio of two to one and also if they sound similar, the same. And actually what happens across cultures is that people take a an octave and then split it in different ways. In the western tuning system we split it into twelve, and you have twelve notes making a chromatic scale. In other cultures like Gamelan music in Bali it’s actually split into five or seven.

When you listen as a person who’s enculturated to one or another system, it’s quite your system, what you’re used to hearing seems perfectly logical and when you listen to the music in another tuning system it might sound a little bit foreign or exotic. And that’s already going to influence very much how we perceive music: what tuning system has been used to compose it.

Another important principle is that of tonality. I sort of threw in the fact that you might be hearing compositions from Bach through to Webern. The emphasis here or what I was trying to allude to is the fact that you’re going to hear compositions from 1700s and ones from the 1900s and basically what happened in the 1900s is that these composers often decided to not stick to tonality. What is tonality? I talked about tuning systems; tonality is basically the fact that within all the pitches that we decide we can play music with you often compose music such that it only takes a selection of those pitches. There’s a hierarchy of pitches that are used to compose the music and the idea is that compositions revolve around a tonic, a sort of central tone, and lots of musical cultures exhibit tonality in that they revolve around a central tone. But again, how these tonalities look across different cultures can be very different, and like I said, even within a culture some people, some of the composers choose to use it, others don’t. What it means is that your perception of a composition that is tonal is very different to one that isn’t tonal because in one case you can make predictions as to how music is going to unfold because you already have this hierarchy; in another case you can’t.

Having introduced this idea of tonality and tuning systems I’d like to now, much later, actually volunteer or sort of give a definition of music perception. And music perception has been defined as just the process whereby we sort of organize, identify, try to interpret musical information so that we have a representation of it and so that we actually meet some sort of understanding of it. It happens in a range of different time scales: so we’re listening to music now but we’re also sort of still listening to the same music, you know, tens of minutes later sometimes in the case of multi-movement composition. What’s interesting for researchers is to try to understand music perception in all these different time scales. For instance, you might care about what’s happening on this scale like hundreds of milliseconds, what can we actually do with that information. Well, we can decide whether what we’re hearing is a violin or a flute and that’s because psychological research has shown that we have these dimensions that we use to try to distinguish between these instruments.

One of them is the attack time, when you play a note in an instrument how quickly it reaches the full intensity of the sound. In the case of, let’s take a piano, for instance. It has a very short attack time: you hear it, it gets loud very quickly and then it sort of recedes again. Compare that with a flute where it takes a while to build up to its full intensity. That length of the attack time actually allows us to distinguish them. Something else that allows us to distinguish them is basically how much energy there are in the higher frequencies of the sound. It’s worth mentioning that any natural sound actually has a fundamental frequency – the lowest – and also a range of other frequencies what are called partials above it. Depending on how much energy, how intense those sounds are in the higher frequencies an instrument can sound brighter or less bright, and again, we can use that to determine whether we’re listening to this one instrument or to the other, so that’s kind of happening very quickly actually.

Of course in perceiving music we’re also picking out things like melodies and that may take place over a few seconds: you decide that this is a melody. How do we represent that? We don’t just memorize pitches and say – oh, that’s frequency 440 or 466, rather we extract often just relative pitches and the contour. What we care more about is whether the melody, the notes go up and then down and then up again and down for a long time etc. So the idea is once we have that representation we can use it as a template or something important with which to sort of keep processing the music that we’re hearing and so we have attention and memory processes coming in when we start to try to make sense or perceive music’s long-term structure, a large-scale structure.

In terms of the methods that we can use to try to understand music perception basically there is a whole range. You could say: well, I’m just going to do behavioral studies and ask people to tell me what they hear. You could decide to do neuroimaging studies, of course, and try to see what’s happening in the brain when manipulating certain features of the music, but there’s a whole bunch of others approaches you can take. You could say: well, I want to carry out cross-cultural studies because they care about how being in culture as in a tonal system, for instance, influences how you then perceive this given sound, so if we take two people of different cultural backgrounds, different cultures, different musical schemes, how do they process this differently. That can be very enlightening. You could also study infants or children. Why might you do that? Well, you want to see how a musical perceptual abilities develop over the lifespan and that’s how we know, for instance, that sort of sense of tonality, those rules guiding tonality start developing in children about four to seven. Before that they’re actually quite open and they’re actually better than adults in lots of things. But then you could also use study, you know, across species and that’s for instance how we know that octave equivalency, this thing that we have where two notes sound the same if they’re an octave apart, frequency ratio of two to one, that’s how we know that rats and actually monkeys have the same ability. I guess, you could say that research into music perception can really be approached from a whole bunch of different perspectives. Part of the interest is actually bringing together all these perspectives, to try to understand how it works in general.

There’s lots of things we don’t know. What I haven’t talked about is the research that – I haven’t talked about a lot of research that I’ve done but there is some work I was doing a few years ago. It was looking at individuals of the disorder known as congenital amusia. These individuals will show difficulty recognizing that that song I’m singing or maybe humming is ‘Happy Birthday’. Most of us know this tune, ‘Happy Birthday’, we’ve been hearing it since we were one perhaps, but these individuals would have difficulty with that. We carried out a series of studies to try to understand why that might be, why they have these difficulties, and just to give an idea of what we’ve found, well, the first question was do they have difficulty learning the structure of the tonal system that they’ve been exposed to. What we found out was that it wasn’t that simple. They seem to be able to learn structuring of tonal sequences just as well as controls. We then asked: well, even if they aren’t able to explicitly say that they’ve heard a wrong note in the melody for instance, is it possible that they’re implicitly processing it? And interestingly what we found was that that was the case, so they were actually able to recognize implicitly that that note is more unexpected in that context than the other one in the context being in the melody. And then we did some EEG to show in fact that the brain is tracking information that they can’t consciously report.

So we found out that there might not be conscious awareness of the information that they actually do have but that sort of question then opens up a whole new bunch of questions and in the end I guess you have to decide what you study at any one time. But in terms the broader question of are there any outstanding questions I guess it depends on where you decide to focus. I already said how many different approaches you can use to study music perception. Those people who work on looking across species will have tons of questions within that. I’m currently working a lot on emotion and music induced emotions and basically with every experiment that I carry out there are five different follow up experiments that I need to carry out to satisfy my curiosity.

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