Okay, before we get into great guitar tone, the question is be asked what is tone? Well, you probably already know that sound is just variations in air pressure, kind of like when you drop a pebble into a still pond, the ripples emanate out in all directions. Now if you had a pure sine wave tone, then it would look like this on a mess telescope. Now a sine wave oscillating at exactly 440 times a second, we perceive that as an A, on the musical scale, but if all musical instruments created the sine waves for their pitch, we would have a very very boring musical lock. I mean, listen to all these different musical instruments or making the same note The reason that each instrument sounds different is that while they're all playing that fundamental a that 440 times a second, they also have other parts of the instrument, either highlighting or cancelling out a number of overtones and harmonics just above that fundamental in a string instrument like this, it is not only this, the single back and forth of that a there are 140 times a second.

It's the multiples of those frequencies, that that string also vibrates, and the vibrations in sympathy of the body, the neck, and all the other hardware on that particular guitar. Now, let's go and see the exactly what happens to the vibrations of a string and we'll look at the open a, of your guitar. Now, disclaimer here. I might get a little geeky in this section, but I think it's Swift, interesting about all the math that is around us musically and how it comes into play when you plug in a nice juicy overdrive in your guitar chain. The math is really, really interesting. If you hate the math, I know you can fast for the section here, but I think it will really open your eyes about how tones are made.

It's super interesting. Here's a side view of a guitar with three pickups at bridge and and not comprising the full length of the playable string. So if we were to play an open a on a guitar, you might know that the fundamental of an open a is 110 hertz, it would sound something like this. We call it 110 hertz because the fundamental is moving back. That string is vibrating back and forth 110 times a second. This is called a closed or fixed boundary wave.

The two ends of the string are fixed at the bridge and the nut These spots are called nodes. Nothing is moving at a node, the area that's moving the most, which is right in the middle is called an anti node. And this whole waveform is called a standing wave. But here's the thing. There are other vibrations happening along the string at the same time. The second harmonic has another node right in the middle of the string.

Remember, we have nodes at the bridge, and then that added a third node right in the middle of the string. Now, what's right dead center of the string length Do you think it is? You bet at the 12th fret, that little area where you have those two dots on most photonics? It's a special part of the neck which is exactly half the distance from the bridge to the nap. So this second harmonic is two times the frequency of that fundamental in this case, that will be 220 hertz and his words gets interesting. If you've ever read Get your finger over the 12th fret don't push it down on the fretboard but just rested over there.

Here's what it sounds like. And you can hear that it's an octave higher. But do you ever wonder why that sounds that way? Well think about it. If you rest your finger directly over the 12th fret, you're completely deadening, the anti node of the fundamental, but you're allowing that second harmonic to ring out because you're resting your finger on a node right in the middle of a string. It's watts, it's 220 hertz, and it's effectively muting the fundamental because your finger is kind of putting a wet blanket at the anti node of the of the fundamental.

Let's move on to the next one, which would be the third and in this one, we've divided a string length into thirds. We've added another node Right, we have a note at the bridge, and then that we've added two more for a total of four notes. And guess where that lands right on your seventh fret. So if you rest over the seventh fret, it'll sound like this, which is an octave and kind of a half, which is a fifth, I won't go into the math right now. But that is now allowing what actually is not allowing the fundamental to move. It's not allowing the second but it's allowing the third harmonic to happily move around because you're placing your your finger right over that node and those anti nodes on that third harmonic there ran out fine they had not on the fundamental and the second one, and then if we go on to the fourth harmonic, that is dividing a string length into into quarters.

And guess what would happen there that would go up if you doubled and then we double again, that would be two octaves, right? So if you play Your finger right over that fifth fret, just rest on that. That is double. Sorry, that has gone up two octaves. Again, the fundamental is muted, the second is muted, the third is muted, because you're basically putting a wet blanket over all of those harmonics. But the fourth one in this case, is ringing out.

Then, of course, this fifth, sixth seventh, and it goes on and on from there. You see this when you play harmonics, there's that word again, right harmonics. On your guitar, you rest your finger on the 12th fret, and it disturbs the free flow of the whole string, but allows the second and the fourth and the sixth harmonic to ring out like this. Now you notice a few things, the pitch is an octave higher. And that's not a surprise because when you double the frequency of the pitch goes up an octave. But you'll also notice that the fundamental has been silenced because we're prohibiting it from moving at its anti mode right here.

This is the crest of the wave right here, the part of the string that moves most of that hundred and 10 will actually that standing wave 110 we're stopping it right here. But the second harmonic, and even higher harmonics can just ring out. So we're stopping the stopping the main one, if you just get off the 12th fret, they're just basically dead in the string. But if you put it right there, those higher harmonics were ringing out. it's sometimes hard to imagine all of these harmonics, and various waveforms going down the string at the same time because of string can only be in one place at a time, right? This might be what kind of what it looks like.

Now in terms of what's going on down a string, when you think about it, when you pluck a string, all those overtones are being generated and they they go down to the knot and they reflect back, sometimes compounding certain frequency and sometimes cancelling others out when you think about it. Multiple harmonics form a compound waveform like a waveform like this plus a waveform like this ends up being a compound waveform, which is kind of the sum and difference of those waveforms. So if we were to just gently pull a string around the 12th fret, we'd basically be just hearing that fundamental model of this harmonics, but as the further you get back on the string, and the more you hit that string harder, then you'll get higher harmonics. So and doing things like palm muting. You can hear they mute those harmonics because most of those harmonics are living back here as well.

You also you pick up his back here now to demonstrate what's going on in terms of Even harmonics, let's see how distorting a signal can throw all sorts of harmonics and why some types of harmonics are better than others in terms of the way they fall in a musical scale. Let's compare a sine wave with a square wave a sine wave is a very pure way, form, the square wave tends to throw off a lot of harmonics. This isn't the sine wave. And we have only the fundamental at 440 hertz. Notice there's no harmonics to the right hand side of that, it's just that fundamental that compare that to the square way. Over on the square wave side, we have a fundamental in the same way for 40 hertz, but we also have a number of harmonics and when I click down, you can see where all those harmonics lie.

That's the fundamental and you can see this The third one is what it sounds like. Because the fundamental third the fifth, seventh is kind of added soon, not kind of added soon. So a 11th there so you can see that there are absolutely no even order harmonics, which tend to fall a lot better in the musical scale than the odd order harmonics that are thrown off on a square wave. So why are you asking my going through all this math? are you screaming at your screen right now? Well, this goes right into how guitar tone is produced.

The right type of wood in your guitar resonates at pleasing overtime the right pickup placement and the pickup selection emphasize the either you know more of those harmonics or less. Even distortion actually introduces overtones and some of that distortion provides better overtone content than others and wouldn't you know when you overdrive a vacuum tube, it tends to emphasize even order harmonics. Ones that tend to fall within that musical scale and sound pleasing to it is, you want to see how it works is really, really interesting as you'll be pretty busy slide, but basically what we're going to be doing is taking an original sine wave input, putting it through some of these effects these overdrive and distortion and see what happens on the app viewer on the bottom right hand corner, which is a spectral view. Basically, what it allows you to do is see what kind of overtones of harmonics are thrown off as we take this original sine wave and place it through these effects.

Remember, a sine waves only have fundamental they don't have any harmonics. So let's start out with the original sine wave. As you can see, there's the fundamental there's no harmonics at all. Let's drop in an overdrive and see what happens. Now you can see we have a second, third, fourth, fifth, six harmonics and they go down In volume, this government to burner that tends to be more even order harmonics and the harmonics are louder. In that case.

Let's go over to the absolute balls out distortion. harm of harmonics you can see that and as we add more drive, it tends to accentuate the odd orders, run even orders. The harmonics are louder and there's a lots more of them. Is it any surprise now that we crave that rich sound of a two vamp or that particular tasty overdrive or distortion pedal? When you start to distort a waveform it starts to throw off all that good stuff. It's actually hilarious how the holy grail of Elliot guitar amplification was just to cleanly make a guitar louder to compete with the rest of the band.

Distortion back then was the enemy but once the guitars started to hear all the richness of certain types of distortion we were. We were hooked once girls. Now there are certain types of distortion that sound better than others. And we'll look at that in detail later. But now you know why distorting guitar signal, that's a good thing. Now there's another part of time that we'll come across that has to do with dynamics, which is how hard or soft we're playing even on an acoustic instrument like this, have a listen to not just the volume of how hard I'm hitting, but what happens to the time when you hit the strings harder.

So when you play it softly has a deeper sound more of the fundamental, you hit it a little bit harder. The more of those harmonics. The more you play it back here. The more those harmonics tend to run out. Now you can in an electric guitar You can start during your dynamics, obviously, just by your plane as we're demonstrating a moment ago. But also you can do things like set volume pedal or even adjust your dynamics automatically with things like a compressor, and a sustainer.

On electric guitar, we also have the ability to, like we said before, we can move out pickups to accentuate more of the back end, which will give us a lot more harmonic content. And we can even roll off frequencies using the the tone control either in passive circuits like this, or active circuits. And finally, we have modulation. Now, modulation is just changing a parameter, a part of your sound and we basically have volume, pitch and tone, right. And if you were to use a modulation, that means you're tweaking a parameter, something about the pitch, the volume or the or the tambour of your sound like a good example. A wire wire pedal, you're modulating with your foot back and forth.

When you put that channel back and forth. Basically, what you're doing is you're sweeping a boosted frequency right across the band to get to accentuate that wah wah kind of effects, you can do that manually, you could, you know, move a knob with you with your hand, but your hands are normally pretty busy. So a better way to do that is use an LFO. an LFO is a basically like a waveform that will modulate one of these parameters for you. We'll go through all of this, but a good example is that say, a chorus pedals like that chorus pill is a very short delay, and that delay time is swept back and forth. So it's a longer delay, shorter delays, longer delay, shorter delay.

And when you put those delays together, you get a very, very rich sound. We'll get into a whole bunch of that. But before we do that, let's get into everyone's favorite subject which is guitar