From Bach To Beer Bottles, The Physics of Music

Why does a saxophone sound different from an oboe? How do tiny flutes produce such loud sounds? Dr. John Powell, author of How Music Works: The Science and Psychology of Beautiful Sounds explains musical acoustics and more.

IRA FLATOW, host:

You're listening to SCIENCE FRIDAY I'm Ira Flatow, and now a little musical interlude.

(Soundbite of a violin playing)

FLATOW: What makes this violin sound so soothing, and this violin...

(Soundbite of a violin playing)

FLATOW: ...so scary? What's the difference between a noise like this?

(Soundbite of a knocking sound)

FLATOW:... and a note like this?

(Soundbite of a piano key)

FLATOW: Why does some music sound sad, other music sound happy? What makes guitars and banjoes sound different from each other? How do tiny instruments like flutes produce such loud sounds? Lots of elements go into making great music, sturdy instruments, artful musicians, catchy melodies. But a lot of what makes music good is actually physics.

Dr. John Powell is a physicist and a musician and he's author of a new book, "How Music Works: The Science and Psychology of Beautiful Sounds from Beethoven to the Beatles and Beyond" and he joins us from Nottingham in the U.K. Welcome to Science Friday.

Dr. JOHN POWELL (Physicist and Musician): Oh hi Ira, it's nice to be on the show.

FLATOW: Thank you very much. Well, what got you interested in this, because you were a physicist and a musician?

Dr. POWELL: I trained as a musician in the old days. I wanted to be a rock guitarist like everybody else but there's a long queue for that job so I ended up being a scientist.

FLATOW: So what did you discover about what the difference between a noise and a note is?

Dr. POWELL: Well it's quite simple really. Your ears are like tiny trampolines and they, sorry not your ears, your eardrums are like tiny trampolines and they bend in and out as the pressure waves from either a sound or a musical note reach them. And the best way to imagine what's going on is if you look at visual waves that you can see like sea waves. If you're standing on a beach with waves coming toward you and running over your toes, if the waves are equally spaced and the same sort of size and they make a nice pattern then your ears would see that as a musical note.

But if the waves are coming from all directions at random intervals and there's lots of - it's basically noisy. And that's what your ears perceive as noise so a musical note is just a noise that repeats regularly.

FLATOW: So why do different instruments, if they're playing the same notes, why do they sound different?

Dr. POWELL: Well if we go back to our standing on the beach analogy you could have waves arriving as a regular pattern but they might be different shapes so you might get very smooth waves at some point or you might get waves with a double top to them or a sharp top to them. And that's what happens to your eardrums. They respond perhaps with a double bounce on a certain instrument or very smoothly with a flute and so on.

FLATOW: How do they, how do our ears recognize what instrument is playing. In fact, you know, you can tell immediately at the first note or two, oh I know that this or that instrument.

Dr. POWELL: Yeah, well, there are a few things that determine how you recognize an instrument. One of the odd things is that you'd recognize an instrument from the own musical sounds that are made just before the note sounds. Obviously you recognize that the note from it's waveform, the different shapes of the notes with different instruments, but there are some unmusical noises that a banjo makes or a violin or a saxophone just as the note kicks in. And we recognize those very quickly. It's very surprising.

FLATOW: Yeah, we have a little experiment, Dr. Powell, to illustrate exactly how that works. I'm going to play a couple of clips and see if our audience can guess what instrument that they're listening to. Let me play the first clip and see if folks can guess what this is.

(Soundbite of a note)

FLATOW: Wow, it sounds like a - to me I thought it was a, you know, an electronic piano but that's not what it is. Let's play the second clip.

(Soundbite of musical scales)

FLATOW: That's what that was? Those are the same notes from a banjo obviously.

Dr. POWELL: That was a banjo. What I did I was told - I read the books about it obviously and I was told that if you cut the very beginning of a note off of a recording it sounds completely different. You can't identify what instrument is comes from. I didn't quite believe it so I got some recording equipment in my bedroom and I got a banjo so I recorded those few notes and just clipped the very beginning off each note and it turned into that noise that you heard earlier which to me sounded like some sort of synthesizer. It was actually just exactly the same recording with the beginnings of the notes clipped off.

FLATOW: And so we, that beginning of the note is very important to recognizing what the instrument is?

Dr. POWELL: Yeah and the other thing is that we recognize what's called the envelope, which is how the loudness of the note changes in time. For example a harp note, it's a twang and it starts suddenly and then it dies away. But an instrument like a violin the actual note starts more slowly and can last for a long time without dying away. And those are the other things that we recognize instruments by.

FLATOW: Talking with John Powell, author of, "How Music Works". Our 1-800-98-8255 you can tweet us @scifri, @-S-C-I-F-R-I, 1-800-989-8255. "The Science and Psychology of Beautiful Sounds." Is there a lot of psychology behind it?

Dr. POWELL: Yes, well there's a lot of how the brain's developed to keep us alive involved. And there's a lot of psychology in that we're actually trained to respond to certain combinations of instruments with different emotional responses. For example, if we hear slow violins with piano on top, film music has trained us that that's a romantic feel. So, you know, it's actually a sociological-psychological effect. There's nothing physical about that. There's nothing particularly romantic about slow strings and piano, it's just that we've seen it so often when people are kissing, you know, when various stars kiss various women.

FLATOW: Right, you mention in your book this fact and this is interesting also that ten violins, when they play together, only sound twice as loud to us as one violin does. Why is that?

Dr. POWELL: Well it's not specific to violins. Any instrument it's true of -flutes or whatever. If you got say ten violin players on a stage and one of them starts playing you'll hear that quite strongly and, as I say, the tiny trampolines in your ear will bounce in and out as the pressure waves arrive. When the next violin player starts playing his waves won't arrive at exactly the same point as the other one.

And so you've got one wave pushing your eardrum in and the other one might be pulling it out again at the same time. Now your eardrum can only go one way or the other and so what happens is a lot of the noise from the different instruments cancels each other out. They're not all pushing at the same time basically.

That's only half of the thing though. The other half is that all of our senses are designed to give us diminishing returns. That's why four smelly socks don't smell four times as smelly as one. Or if you're in a cave and it's dark and you light one candle it makes much - a really big difference to your light, whereas if you lit a ninth candle rather than having eight going that would make a much smaller difference.

FLATOW: Right.

Dr. POWELL: And so all of our senses are designed to notice very small changes when the stimulus is very low, but as the stimulus gets bigger we ignore it more and more.

FLATOW: Very interesting, 1-800-989-8255 let's see if we can get a phone call or two in here. Let's go to Chris(ph) in Craw(ph), South Carolina, hi Chris?

CHRIS (Caller): Hi guys how's it going? Enjoying your show, real good.

FLATOW: Thank you.

CHRIS (Caller): I just wondering if you guys had input on - he's talking about the tendencies how we pick up real small details. Why they changed the tuning hertz from 444 to A440 or, what was it, 528 on the Solfeggio scale?

Dr. POWELL: Yeah, I do happen to know about that.

FLATOW: Thanks, Chris.

CHRIS: I'll take my answer off the air.

FLATOW: Thank you.

Dr. POWELL: Hello?

FLATOW: No, he just took the answer off the air. You heard his question, right?

Dr. POWELL: I did, yes. Yeah, so it's an odd thing. An A is an A all over the world. If you buy a clarinet or a flute in Tokyo or New York or London, the A on it will always be the same, the same frequency. Now if you ask people about this they generally thing that the note was decided upon by Beethoven or someone centuries ago for musical reasons.

But in fact, the notes were chosen in London in 1939 by a committee, very unmusical. And the reason why they chose a particular note is because they had to use one note. It didn't really matter whether it was A440 or A444 or 448. All those notes are equally musical. But somebody had to say this is a standard note, because before that point the people who made flutes and clarinets didn't know how long they should be. Because the length of an instrument like that tells you what note it's going to give off, and all over the world at that point all the clarinets were different lengths. And so it wasn't actually a decision for musical reasons. It was a technical one. Basically the engineers who made the instruments wanted to know how long should these instruments be? And they chose 440.

FLATOW: 440 is what?

Dr. POWELL: 440 vibrations per second, that's the rate at which the waves arrive at your eardrum and they just chose it because it's a nice round number near the middle of where everybody around the world was using for A. But 448 would have been equally musical. It's just that somebody had to decide something and they decided on 440.

FLATOW: It's amazing a committee arrived at something.

Dr. POWELL: Yeah, right, right - in 1939 as well.

FLATOW: Let's go to Philadelphia, Richard, hi welcome to SCIENCE FRIDAY.

RICHARD (Caller): Hi Mr. Flatow, thanks a lot. I have a collection of music that was given to me by a friend on an MP3 and I've realized that I've been deleting songs off it that I wasn't getting a strong enough happy vibe off of. And I was wondering what is that always you to discern that music is making you happy and it's not like it's toe tapping, because there's a lot of stuff that's risen, but there's literally this emotional response I derive out of the notes, and it's like, wow, this is just not happy enough that I need a happier song.

FLATOW: Yeah, yeah. You wouldn't be listening to music if it didn't drive an emotion.

RICHARD(ph): Right, right.

FLATOW: Yeah. So what makes - good question. Thanks, Richard. What makes some music happy to us and others makes us feel sad?

Dr. POWELL: Well, it's rather a big question, but I'll do my best.

FLATOW: Give it a shot.

(Soundbite of laughter)

Dr. POWELL: Right. Western music uses a lot of harmony. It's the only music that uses harmony because, you know, we use chords to accompany our tunes, and we can make the chords anxious and because what you've got when you got a chord is three notes or more, all joining together to form a combined wave that's vibrating in and out. And if the notes in the chord are all collaborating with each other and being, if you like, friendly to each other, then you get a nice warm effect off that chord. If you join some notes in there which don't agree with the other ones, as Hitchcock did in the "Psycho" film music you played earlier - I think that was "Psycho," wasn't it, you were playing? But that ee-ee-ee sort of horrible jangly sound you get is from notes which actually are competing with each other for your attention, and that's how you get anxiety into your music. And lots of composers in films or in pop songs or whatever can build some anxiety in, and then they release it by coming back to a much more open, friendly chord, if you like.

FLATOW: Yeah.

Dr. POWELL: And so you get - you can have anxious music. There's no doubt about that. And also there's - various rhythms are more jolly than others, but the actual emotional effect it has on you can be a combination of these effects and your memories of various things.

FLATOW: We have a couple of clips here that illustrate what you were saying a little bit about the two notes being next to one another and notes being an octave apart. And I want to illustrate what you had to say. Let's play the two sounds. First, the two notes that are a whole octave apart, and the second are two notes that are very close together on the scale.

(Soundbite of music)

FLATOW: Wow, very different.

Dr. POWELL: Yeah.

FLATOW: There's a whole - what is that wobble in the two notes that were close together?

Dr. POWELL: The wobble is - if you imagine walking down a street with a friend who's got a slightly different pace than you have, and let's say he's taking 13 steps to every 12 of yours, that means that for most of the time you'll be out of step with each other and then occasionally you'll come into step with each other - every 13th step in that case. And so if you're, say, photographing that, you'd see the two people out of step all the time and occasionally they come into step. And what's happening with those two notes is that they are very closely matched. They're just out of step with other, and they come into step what sounded like every twice a second there. It's going wa, wa, wa, wa, wa, wa. And the volume goes up - the sound you hear - as the notes fall into step with each other. It's a fairly horrible effect.

FLATOW: Wow, wow. I'm Ira Flatow. This is SCIENCE FRIDAY from NPR. Talking with John Powell, author of "How Music Works: The Science and Psychology of Beautiful Sounds, from Beethoven to Beatles and Beyond."

Of course, you can experiment with some of those steps, out of step. You know, Dave Brubeck made a whole career out of making music that's slightly out of step but, you know, still sounds very pleasing to the ear.

Let's go to the phones. 1-800-989-8255. And let's take a call from Rob(ph) in Nevada City, California. Hi, Rob.

ROB (Caller): Yeah, hi. I have a question that sort of relates to the last question a little bit. Neurotransmitter research has now shown that rather than the stable key lock theory, they think the keys vibrate in and out of the neurotransmitter locks at audio frequencies, singable tones, in a sense. And I wondered if he had a comment on that, in the fact that there are probably tones going on the neurotransmitter level. And also, if you have a harmony, you have rhythm. And so rhythm would be involved. In a sense, if something is out of tune, it's also out of step, out of rhythm.

FLATOW: Right. Let me get one question at a time because there's a lot of concepts.

ROB: Okay.

FLATOW: What about - thanks, Rob. What about the relationship between music and neurotransmitters? Any work done on that?

Dr. POWELL: I'm sorry, no. I haven't done any work on that. I think the best thing to do is when you don't know is to say you don't know.

(Soundbite of laughter)

FLATOW: Good answer. And what about harmony? He was asking a question about harmony. That is a pleasing thing - harmony - as opposed to the wobbles we were listening to before.

Dr. POWELL: Yes. Like I say, as I said earlier, harmony doesn't always have to be harmonious and nice. You can actually have harmonies which give you some anxiety or tension. And then you release that, and it's very straightforward, the way that the waves build up to give you this tension. And it's quite straightforward as well how you get the ones which make you relax.

FLATOW: You have an interesting part about perfect pitch. People with perfect pitch.

Dr. POWELL: Yeah.

FLATOW: And you say that - first, tell us what that is. And you say that if you listen to music earlier in life, you may have a tendency to have it more.

Dr. POWELL: Yes, it's true. Perfect pitch is the ability to remember notes, the actual frequencies involved. We all remember songs like "Baa, Baa, Black Sheep." But I start and you will stop probably on any note you like, any note within your range. But if someone's got perfect pitch and they've heard their mum play "Baa, Baa, Black Sheep" on the piano using - starting on the note A, say, they will remember the note A. And they will be able to sing actually the notes involved, not just the jumps between them. We can all sing the relative pitches, the jumps between the notes. We all do that quite accurately. But we don't actually start off on the correct note, unless you've got this thing called perfect pitch, which is a memory thing, which happens generally before you're six. And people think it's associated with having great musical skills.

FLATOW: Right.

Dr. POWELL: But perfect pitch is not a very musical skill. It's not very useful. In fact, it can be a bit of a pain because you've got the correct pitches and if the person whistling next to you isn't doing the right pitches, it's rather off-putting. But it's an indicator of being highly trained musically because it means that you were doing a lot of music before you were six.

FLATOW: Really? So if you want to encourage perfect pitch, you could try to have your kid take up an instrument or listen to music at an early age?

Dr. POWELL: There really wouldn't be any point in acquiring perfect pitch. Which is why they never try to do so at music colleges. They don't actually train you to get perfect pitch because it's not that useful, because there are tuning devices to tune your instruments. And let's say on a campfire sing-song, there's no need to have your guitar tuned to the correct pitch. You just tune it to what the tunes - what the strings are at that day.

FLATOW: So then you just tune around that note.

Dr. POWELL: Yeah. But if you're playing with a flute player, you've got to tune your guitar up to the correct notes because the flute can't be adjusted in that way.

FLATOW: Yeah. And he's got - right. He or she's going to have that pitch all day long.

Dr. POWELL: Yeah.

FLATOW: Can you stay with us a little bit longer, Dr. Powell?

Dr. POWELL: Certainly.

FLATOW: We're going to come back and talk more about "How Music Works: The Science and Psychology of Beautiful Music, from Beethoven to The Beatles and Beyond." 1-800-989-8255. Or you can tweet us @scifri, @-S-C-I-F-R-I. We'll be back after this break. So stay with us.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY. I'm Ira Flatow. We're talking about science and the arts this hour - in this particular case, science and music, and the science of music, with Dr. John Powell, who is a physicist and a musician, author of the new book "How Music Works: The Science and Psychology of Beautiful Sounds, from Beethoven to Beatles and Beyond." And I couldn't let you go, Dr. Powell, before you can demonstrate your drinking straw oboe.

(Soundbite of laughter)

FLATOW: Tell us what you have with you and we'll see if we can get it to work.

Dr. POWELL: Okay. There's actually a video of myself doing this on your blog.

FLATOW: Right. On our website.

Dr. POWELL: On your website, sorry, yeah. Yeah. What I have in my hand here is a drinking straw, and I cut the end to a point. It demonstrates quite a few things about the physics of music because things like reeds can produce quite a lot of noise as they flap open and close as you blow through them. And the other thing is that shorter tubes make the higher notes. So what I'm going to do - it's a completely stupid activity. I'm going to put this drinking straw oboe in my mouth and try and make the noise it makes. It's quite difficult to start at times. And while I'm playing it, I'm going to trim it to length with my pair of scissors I have here. So I'll give it a try.

(Soundbite of laughter)

Dr. POWELL: This might not work. We'll see.

(Soundbite of musical notes)

(Soundbite of laughter)

FLATOW: And you can try this at home, right?

Dr. POWELL: You can.

FLATOW: You can.

Dr. POWELL: And you can get your friends to play different notes at the same time.

FLATOW: All right. Thank you, Dr. Powell, for taking time to be with us. A fitting closing.

Dr. POWELL: Thank you very much.

FLATOW: You're welcome. Dr. John Powell is a physicist-musician, author of "How Music Works: The Science and Psychology of Beautiful Sounds, from Beethoven to the Beatles and Beyond."

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