There are a number of audio effects based on a very short delay. And we saw earlier how a comb filter was a short delay. How when you have just a very short delay of the same signal you get a series of notches throughout the frequency spectrum. And just that can actually be quite useful. If you have a heavy distorted guitar, or a really thick synthesizer, that series of notches can help to thin it out and let other sounds through. It's kind of like things peek through the picket fence. They see between the, the notches in the comb filter. But it's static. And very often, we want to put those notches in motion. And that's what I mean by modulated. So we'll have these modulated short delays, in which we have a, a very short delay to create that comb filter, but then we slowly change the delay time, which gives it this nice kind of wash of sound that moves back and forth. It can be used kind of exaggerated for, like, kind of, psychedelic crazy sounds. Or it can be nice and subtle to add motion to kind of a static sound. Very often, what we do is make it do different things in the left and right speaker. Which can take a mono signal, like a guitar, perhaps, and make it sound very big and wide, as both speakers do different things. The effects that make up the modulated short delays are choruses. Phasers and flangers. And they really are creative effects, they're kind of supernatural in a way. There's not really a perfect, natural, kind of analog to them, but they're a lot of fun and they have a great usage in a contemporary mix, so we're going to look at them in this screen movie. So we see that the idea of a comb filter has a major impact on our recording because delays and phase cancellation is all around us. But it's also been used to great affect in audio effects and the effect that uses this greatly is called a flanger. And a flanger really is a comb filter, a slight delay, that's put into motion. By a low frequency oscillator, so let's see what we've done here. I've added a second trace to the spectrograph, so we see a separate spectrum for left and right, and we'll also see a separate trace for left and right in the spectrogram display here or the sonogram display. So first we start with just our noise. [SOUND] . And right now, I have a 0.1 millisecond delay on it. And I'll increase that delay time. And I'm doing this, now, with a flanger. So we're seeing that if I have a flanger with the LFO off, where that's not in motion. I can manually control where those notches are. And hopefully, we're starting to understand that this is comb filtering. What makes a flanger special is that it puts this in motion. And that's what gives it this wonderful, kind of swirly, outer-worldly kind of vibe to it. So if I engage the low frequency oscillator, a cyclic motion applied to a parameter, we'll see we're going to start to get some automatic motion to this. [NOISE] So we can see that a flanger is a comb filter in motion, so we get this wonderful, swirly kind of sound. [SOUND] Now it's very obvious when you see it here on a noise, but this is even more impressive when applied to musical instruments. And a flanger, again, is a just a short delay that's been put in motion by a low frequency oscillator. And very often it's done differently in the left and right speaker to give it a back and forth kind of swirly wide stereo presence. [SOUND]. The next short delay effect we'll look at is a phaser. Now, it's actually kind of tough to put this in this category. Because it doesn't fit perfectly. But I didn't know where else to put it. So a phaser sounds much like a flanger. In that, it's a series of deep notches that move differently in the left and right speaker, giving us a swirling stereo effect. The difference is that the flanger had a strict comb filter. It was even notches across the stereo spectrum. The phaser is not even across the spectrum. And in fact, every DAW has their own way of creating a phaser and their own way of organizing these notches. But what will be the same in all phasers is that it is a series of deep notches across the spectrum. And they will be put in motion, very often differently in left and right. Let's see this in action on some white noise. First, just the white noise. All right. And now I'll enable the phaser. [SOUND] And right now it's like the flanger in that I can have a series of notches that are not in motion if I choose to. But you'll notice that these are not evenly spaced the same way that the comb filter was. The flanger looked just like the comb filter. This one doesn't look just like that. I'm going to now adjust some of the parameters on the phaser. [NOISE] I can adjust the frequency of it, and you'll see how it moves very differently than the comb filter, because the comb filter will always introduce new higher notches when it went down, remember. So this is different from that, but has much of the same kind of effect. With this phaser, I can also change the number of notches there are. And I can modify how they're related to each other. So you see with the phaser we get much more control over exactly where we're going to emphasize. It can be very vowel like in that the sounds it makes can sound like changing vowel sounds of a mouth. And let's hear what this is like when put in motion [SOUND]. So like the flanger we have a series of notches that are put in motion different in left and right. The phaser though is not a comb filter precisely, but it has much the same sound. It's a great effect for guitars and for thick pads, things that are kind of overwhelming in the mix, because you notice with the phaser, I could make it notch out a specific portion of the frequency range in a really interesting way. That could possibly leave room for other instruments in the mix and it can also be a way to make something sound wider by making it sound different in the left and right channel. You ever notice that when a car's coming toward you it's higher pitched and when it goes past you it becomes lower pitched, as it races away? That's called the doppler shift and we emulate that in the DAW, or in our computer, by modulating or changing delay times. I'd like to just show you how this functions by putting a sine wave through a chorus device. And then we'll see how it's changing the pitch of the sine wave. So first we just hear the sine wave, [SOUND] and now I'm going to start varying the delay time. [SOUND] . So we see that subtle shifting in pitch of that note. So again, that is due to a changing in delay time. And the changing in delay time can actually have a great impact on the pitch of the sound. This phenomenon is used to create chorus effects. And the role of a chorus effect is to make it seem like there's multiple performers performing that same part. And they get the idea from a choir, a chorus of people, when they're all singing together they're all a little out of tune with each other and it creates that thick a little bit out of tune sound. And the way it's done it by making many copies of the same signal and then slightly shifting the pitch in all of them. And it does it by manipulating delay times on short delays. So, let's look at how a chorus functions and one of the main things about a chorus that's important is that it changes the pitch differently in left and right. So, you get a much wider sound from the single instrument, so if you want to give the impression that a single instrument is being played by multiple people, a chorus device is great. Let's try it out here, here's with the chorus off, [SOUND] and then I'll start bringing it in. [SOUND] [SOUND] And there you go. Now with a, this is a very simple chorus. Now we're just having, just changing the left and right speaker. And on a sine wave, right now in my headphones, I'm getting this kind of swirly left and right sound. It's very effective at making something sound wide, and out to the sides. Now there are many ways chorus devices are designed. Sometimes there's many, many more copies and they're all slightly out of tune, and the LFO's on each one are a little different. So you get even wider, more effective sound. But that is the fundamentals of chorus. Multiple copies of the same signal with an LFO changing the delay time on each one of them in different ways. So we get a wide shifting character out of it. I'm sure you are already thinking of some musical uses for these modulated short delays and hopefully after hearing the examples on white noise and on simple sine waves you start to realize what you've been noticing before. A lot of learning these tools is being able to describe what you hear. If you know the sound of a chorus, when you hear it in a production, you'll understand what it is, and then you'll be able to apply it in your own music. So it's important to first be able to understand what the device does, then understand what it sounds like and then be able to analyze what you hear in productions and then you'll be able to apply those musically. So we're trying to train our ear to hear these techniques. Now I'd like to give one musical example of using one of these devices. And I'll be applying a chorus to the guitar sound that we've been working with through this course. So let's hear the guitar sound now. [MUSIC] Now, we've added a new type of meter, and it's this Lissajous meter, and what this is designed to do is show us the stereo width of an element. We see that it's going to be a line straight up and down if it's mono, and you'll see lines going out to the sides if there's any stereo presence in the sound. Now let's hear the guitar with the chorus applied. [MUSIC] [MUSIC] Immediately we see that the Lissajous pattern is showing us energy out to the sides of the mix. The spectrograph is showing us energy differently in both left and right. The red and green tracers are doing different things. And if you listen on headphones, you can really hear how the guitar is now way out to the sides of the mix, and we've taken a very mono thing, and made it quite stereo. I'd like to now examine how this is used in the context of an entire mix. I'm going to play the mix we've been working on, but without the chorus. [MUSIC] As I'm listening to that, for me, I feel like the guitar is in the way of the keyboard, in that they're both in the same frequency range, and they have similar timbres. And they're both right in the middle of the mix. So I'm having trouble differentiating the sound of the guitar, and the sound of the keyboard. And that's where I think a chorus could be quite useful. So, I'll play the same exact thing again and then after a little bit of time I'll bring in the chorus and we can hear how that changes the sound of the guitar and of the entire mix. [MUSIC] I'm bringing in the chorus now. [MUSIC] To me, it felt like the guitar moved out to the sides of the mix. And I actually had a better time hearing the keyboard and melody, as the guitars are pushed out to the side. I think it was a good usage of chorus. And guitars are just a great thing to play with sonically. There's no rules on how they should sound. And using pedals and effects is really accepted with an electric guitar. So it's a great place to experiment with modulated, short delays.