The Most Important Lecture

The topics in this 10-minute video include the harmonic series and the physical nature of sound. This lecture kicks off a few of our classes like the music theory class or the effects synthesis and mixing primer. It’s been a while since I gave this talk on Instagram live.

I’ve given this speech a lot and by now I’m quite sure I do it at least an octave better than I used to. But I believe it’s massively important for anyone studying these things to understand. So I’m putting it here knowing full well that most people aren’t going to watch a 10-minute video.

If you understand how this stuff works, you can safely skip over it. But you also probably understand that this is amongst the most important things you can learn. So I’m sharing it with you for free and I hope you excuse the low production value of this video.

It’s inversely proportional to how important I think it is for you to understand. Enjoy. This is amongst the most important lessons that I teach.

This was one of the first things that I was able to sink my teeth into that really changed the way I thought about how sound works, about how harmony works, and I really think that this lesson here is foundational to pretty much everything that we teach in the school. And if I were going to ask you to take one thing away from this lesson, it would be this. Almost never in nature do you only hear one thing.

You’re always hearing an aggregate of a lot of things at once. And that’s actually mind-blowing when you start to think about what sound is. And here’s the reason.

When you hear a sound, you’re probably thinking of things like sound waves or vibrations, but you can’t hold a vibration in your hand, right? Like a wave isn’t a thing that you can put in a box and bring to somebody. What you are experiencing when you hear sound is changes in air pressure.

We’re swimming right now in this soup called air. There’s thousands and thousands of pounds of pressure on you right now. It’s invisible.

You don’t see it. You don’t think about it, but you’re swimming in it. When you hear something, when you hear a fork drop in the other room, even with the door closed, what you’re experiencing is somehow the disturbance in this medium making its way to you through the door.

It’s not like there’s one little molecule of air making its way and walking to you, right? When you throw a pebble in the pond and you see the rings extend outwards, if there’s a leaf on the pond, that leaf doesn’t make its way to you. It just goes up and down as the rings make their way towards you.

So I want you to imagine instead you’re on a crowded dance floor and you’re dancing around and there’s a waiter who’s trying to get through. So the waiter’s coming through with a tray and says, “Hey, excuse me. I got to get over here.” You got your boogie on over here and you move over a little bit, make room for that waiter to come through.

Now there’s somebody standing over here next to you and that person just got crowded. “Oh, excuse me.” Then they move over a little bit too. And as the waiter passes through, there’s now space and you fall back into your space.

And the person next to you comes back into where they were. And that pressure wave is what travels all the way across the room. If that happens over and over again, we experience it as sound.

The trouble is this. If we’re talking about a change in air pressure, we hear changes in air pressure anywhere between about 20 times a second and 20,000 times a second. That’s totally generous.

Most of us don’t hear that. Below that, it’s still sound, but we don’t experience it. Above that, it’s still sound.

We don’t experience it. Some animals do. There’s a limit theoretically to how high sound can go in air because the air can only vibrate so quickly.

But the air is spongy and moves back and forth. You are experiencing within this narrow range. You’re experiencing that as sound.

And you are measuring the air pressure just like a barometer. And in fact, air pressure, when a low pressure front comes in, that’s sound too, right? So the trouble is there is only one air pressure at any point in time.

Think about that. You are picking that up. It’s pretty hard to reconcile then how you can hear two things at once.

And yet we do. In fact, when you hear a piano string vibrate, you hear more than one thing at once. The string is vibrating like this.

So when you have a string that’s vibrating like this, it’s going back and forth. And you are experiencing that as a sound, some single pitch. If you’ve ever pushed a kid on a swing and the kid says, “Faster.” I have two kids and they both say that.

Pretty much every kid gets on a swing and they’re like, “Faster.” But as it turns out, you can’t push the kid faster. You can only push them higher. Because the speed of the swing is fixed based on the length of the string.

If this string is this long and it’s going two, three, four, five, six. If I go higher, one, two, three, four, five, six, it’s going to swing the exact same speed, no matter how high I push it. That’s some Isaac Newton stuff.

And that’s baked into the way the universe works. Instead, what we can do is get the string vibrating at a single frequency. However, we can also naturally get the string to vibrate at multiples of its length.

And here’s where the plot thickens. So I can step back here. I can get this string going like this.

But I can also get it going at the multiple of that frequency. There we go. So what’s happening now is it’s vibrating at the halfway point.

It’s vibrating once like this. Let’s call that 100 times a second. And it’s going like this at the halfway point.

Little math, two to one ratio. So that’s going to be 100 and 200, right? Twice as fast.

The thing is, you’re hearing both of those things at the same time. You are hearing this and this. Like this.

Both of those things are happening at the same time. I want you to watch this. The string on a piano isn’t like a string on a guitar.

I can’t put my finger on the neck and shorten the length of the string and change the pitch. The string is fixed between those two points. But what I can do is I can play the note and I can find the spot along the string right in the middle where it’s going like this.

And if I put my finger right there, what I’ll do is I will get rid of this and leave this intact. And so what you’ll hear is the doubling of the frequency. I’m not creating a note when I do that.

This is the really important part of this. What I’m doing instead is getting rid of the louder lower note that’s underneath it so that you can hear the note on top of it that was there the entire time. Okay.

Check this out. This is a C. Can you hear that?

This note. There it is. That note has been there the entire time as well as if I find the three to one.

That one. So now you’re hearing a G. You heard a C.

You heard another C. And now you heard a G. There’s a C.

There’s a C. And here’s a G. As we go up, the distances will get even shorter.

They get shorter and shorter. They get closer and closer together as they get higher and higher. And this is called the harmonic series.

And it’s true for anything that’s going to make a note. It’s going to be true for a flute. It’s going to be true for a banjo.

It’s going to be true for your voice. You are hearing multiple frequencies at once. If you ever wondered why a C and a G go together so well, why does that sound super dope and that sound a little bit grating?

The reason is the G is baked into that C. It’s already there. The foundation of harmony and the physics behind how we shape sound all starts here.

I’ll also just point out to you that the reason that these little jumps, these harmonic jumps get closer and closer together as they move up, is that the octaves themselves are the loudest part. And that’s every time we double. So if we call this 100, this one is 200.

It’s really, really important to note that this one is not 300. This one’s 400. It’s twice two.

And this one up here would be 800. So we have exponential doublings. When you’re talking about octaves, you’re really expressing that in a logarithm.

That’s a logarithm. In school, for some reason, they make it way more complicated than I think they ought to. But instead of saying, hey, let’s play something in the key of 800, we’re saying, no, that’s it.

Like 800, that’s a C, just like 400 was a C, just like 200 was a C. We’re just saying the first C, the second C, the third C. And those are the octave jumps.

Those are the really loud, very well-reinforced harmonics. If we’re doubling every octave, 100, 200, 400, 800, those divisions of the string, the first division is 200. To divide it in thirds, it’s 300, 400.

And so those increases don’t make it as far to the next octave. The next octave is a big jump. So we get more and more notes.

And you can see that in the way an equalizer is laid out. This informs a lot of what we do in music production. It informs a lot of the way we think about harmony and music theory.

The half of music theory is learned like a language, but the other half of it is baked into physics. If you go to different cultures around the world, you’ll find variations on tuning, certain different notes that are employed. But every culture on the planet employs an octave.

And probably things like fifths and thirds, all the tunings of those can sometimes be a little different than the way we do it for reasons I can’t go into right now. And if we ever found life on Mars, they probably have octaves too. Until some alternate universe somewhere were up and down, and cats are dogs, and day is night, then maybe they wouldn’t have an octave.

It would be a different thing. But the way physics works, as far as we know, is that materials behave in this way. And the fact that you are always hearing multiple things, almost always, when you’re only hearing one thing, you’re hearing a single sine wave.

And you can reconstruct sine waves to basically describe any other wave shape. But when you hear a complex wave shape, what you are hearing is a buildup of lots and lots of different tones. And I’ll just play some of those off the harmonic scale.

And the last thing I’ll do is I’ll point out to you that you should try and listen for these notes, even when I’m not putting my finger on the string, because they’re in there. That’s what I want you to listen for. Let’s see if we can find…

that note in here. You hear it already? I do.

Let’s see if we can find this one. It’s in there. We’ve even got like…

There’s a D. So thanks for coming to my TED Talk. I think I covered most of what I wanted to.

I would love to speak with anyone who would like to join the upcoming class.