5.3 (Part 2) Music Machine

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From the course by University of London

Creative Programming for Digital Media & Mobile Apps

42 ratings

University of London

Creative Programming for Digital Media & Mobile Apps

42 ratings

This course is for anyone who would like to apply their technical skills to creative work ranging from video games to art installations to interactive music, and also for artists who would like to use programming in their artistic practice. This course will teach you how to develop and apply programming skills to creative work. This is an important skill within the development of creative mobile applications, digital music and video games. It will teach the technical skills needed to write software that make use of images, audio and graphics, and will concentrate on the application of these skills to creative projects. Additional resources will be provided for students with no programming background. At the end of this course, you will be able to: * Write creative, audiovisual programs in the Processing environment that run on desktop and mobile * Programatically manipulate sound in creative ways * Display images and image sequences * Generate interactive, algorithmic graphics * Work with a 2D physics engine to create a basic game

From the lesson

Music Machine

Welcome to the final week of Creative Programming for Digital Media and Mobile apps. This week, we are going to move back to one of our favorite areas of app development - music apps. We have a very special guest this week - Martin Roth from RJDJ. Martin has lots of experience working on consumer mobile music applications, including the amazing Inception app, and The Dark Knight Rises. He shares his views on the expanding space in mobile music applications, and offers us his opinion on the WebAudio API. Meanwhile, Matt will be showing you how to create a very basic drum sequencer, and Marco will take you through the basics of sliders and multisliders, which are particularly useful for controlling parameters in music apps. Mick will then be taking you through some synthesiser examples in WebAudio, and talk you through the Music Machine example, which is a great place to kick off making a professional interactive music app for mobile.

5.1 Basic drum sequencer9:09

5.2 Slider widget7:32

5.3 (Part 1) Music Machine discussion with Martin Roth from RJDJ7:42

5.3 (Part 2) Music Machine32:52

Meet the Instructors

Dr Marco Gillies
Senior Lecturer
Computing Department, Goldsmiths, University of London
Dr Matthew Yee-King
Lecturer
Computing Department, Goldsmiths, University of London
Dr Mick Grierson
Reader
Computing Department, Goldsmiths, University of London

[SOUND].

Okay. So as you know, we were just talking to

Martin, and he was telling us a bit about RJDJ.

We've heard from Marko. Marko's been telling us about how to use

sliders. and we've also done some stuff last week

on sliders and building them and stuff. And, you know, Matt's been doing this

stuff with you about, playing back sounds in rhythm to a sequence.

So, what I'm doing is I'm going to show you an application that we developed, I

just briefly touched upon with Martin. I'm just going to I'm going to set it

running again for you. But I want you to just kind of pay

attention to the little things I do. As I'm doing them, I'm going to briefly

explain what they are, then I'm going to go through the whole application in

detail. Explain how it works.

Then we're going to discuss it with me and Marco and Matt at the end just so

that we can make sure we've got everything covered.

This is like a fully fledged music application.

It's sonically quite advanced. It's just bare minimum on the user

interface, it just has the interaction, so you could use quite a lot of the

techniques that are in this to make your own thing.

But let's just see what it sounds like again and see where we, we are with it.

[MUSIC] Okay, here we are. So you can hear we've got a drum machine.

Let's just turn the two synths down, so we can hear these these, these drums

here. We've got a bass drum, we got a snare

drum and you can see, I'm pointing at a snare drum hit.

[MUSIC] That one and that one. And there's a blue line that tracks

across telling us where in a drum beat we are.

The second line in the drum, in the drum machine is this.

You hear that? That's the

[INAUDIBLE]

the clap. So the claps going on the in between

beats in between the base and the snares. You got a classic techno feel.

And as Matt was saying all of the sounds we're using come straight from your

standard kind of 808 or 909 drum machine and thereof [MUSIC] So, what else can it

do? Well, we've got two synthesizers.

We can play these [INAUDIBLE] synthesizers individually, and we can

vary a whole range of parameters for them.

They're fully fledged synthesizers. We can write waveforms for them.

If you're interested in synthesis and you know a little about it I think you'll

find this one interesting. But if you don't, it's still really

usable and I need you to get your head around it.

We can write waveforms, we can add a filter, we can change the quality of the

filter. Now let's just have a listen to the

filters, I'm want to turn one of them up. [MUSIC] So here's one of the synths.

I'm going to change the filter. [MUSIC] [MUSIC] I've also got this

resonance. And this filter out.

We could also change the release and the attack.

So we're giving it an envelope. And it creates that kind of acid techno

feel. If I change the attack actually with

something like this. [MUSIC] Just makes it quieter.

We can transpose any of the channels. So I'll change the key of the entire

sequence. And then again.

And then if I want [MUSIC]. You just go back to where you were, more

or less. and also, I can add some delay.

[MUSIC] And I've got a second one here as well.

Now, the beat that I'm altering at the moment is the actual [MUSIC] [INAUDIBLE]

sequence of notes that it plays. Now, I can select a sequence of high

notes, like this, or a sequence of low notes.

And just like in the example that Matt was showing you [INAUDIBLE] [MUSIC] Drum

machine. There's 16 steps, so I can change two of

the notes. There you go.

I've got the fill trap as well and I'll do this stuff.

[MUSIC]. That's quite pleasant.

We have resonance. [MUSIC] That's distorting quite a lot.

I don't really mind. I can add some more delay.

[MUSIC] Add a few claps. [MUSIC] And some more snares.

Maybe a cymbal.

[MUSIC]

You gotta take, So that's a basic music machine.

[MUSIC] It's a common thing that you can easily sell on the upstart for, I don't

know, actually music apps. Let's talk about this for a minute.

Music apps go for quite a lot more money than other kind of apps.

You can sell an app like this for much more than three quid on the [INAUDIBLE]

on the IOS app store. You can probably sell it for five to six

pounds or more. Or if you're in America, that would be

dollars. I imagine that like $8 or $9 out of

[INAUDIBLE], what is, what are pounds and dollars anyway?

Who cares? Anyway, they're much more expensive and

they're much more specialist but they're still they're still really useful.

And I think something like this, I mean as something really famous, well, there's

a really famous [UNKNOWN] app which is built on, based on a and old-fashioned TV

R3 synthesizer and a nice [INAUDIBLE] drum machine in which still sells in it's

droves. And all the people do is complain about

how unusable it is. So I'm not that worried that ours is

knocked out quite quickly. It is knocked out quite quickly, but it

is powerful, and you can build on it to do more interesting things.

And you could use some of the other stuff we've done to play some loops.

By there are some complexities to this and I want to show that you know, what

they are, so I'm going to quit this temporarily and just go back to the basic

version before I continue with that. Just see you can see in the most simple

possible way what it is that we're doing. So you go all this stuff for free as I

was describing before. as I've said every week, you know, you

can just go to your lessons. but this time we're in week six.

Week six has got a bunch of small tests in it.

It's got a small drum machine, and t's got this thing called synth test.

So, we're going to have a quick look at this synth test.

Just because it's a easier code to, to look at.

It's got the gooey code in it. it doesn't have the drum machine it just

has one synthesizer. and yeah.

There you go. It's just one of the synths.

[MUSIC] [MUSIC] Now, [COUGH] so you can see here it's the same, and it basically

allows me to set the pitch, change the filter, change the resonance.

Same old same old. Let's have a look at it.

So we start off as we normally start off by declaring a maxim context.

If I can just make this a little bigger so you can see.

so this is what's happening on the audio. Behind it, as, you know when Martin was

here we were talking about the web audio api.

So, behind this is all web audio. And the maxim js, the maxim js file,

which is here has got all of this stuff in the background.

Now, if you're interested in this sort of stuff, and you want to learn more about

how we built Max and JS. You can always post questions on the

forums. And the TAs will manage those and any

really important questions where we feel we've got some material we can really

help you with we can point you towards a good answer.

And also there are lots of other places like musicdsp.com and other sites like

that can help you understand what it is that's gone into building this.

But you don't really need to if you just want to get started.

We just have to have a context, and Maxim provides the context.

Also, we've got an audio file player. Actually, we're not using that here, so

that's not going to matter. Instead of using the audio file player,

which is what we've been using most of the time, we're using a synth.

So, Maxim can have a synth and I've called this Synth waveform.

Now, the thing about a synth that makes it different to an audio file player is

you can write in an array of values between minus 1 and 1.

And that will define the texture of the sound which you're creating.

Now, most synthesizers have a number of different wave forms.

And there's lot of different approaches to creating wave forms.

Um, [COUGH] and in one of the other examples that we've got in this folder

there's a really easy way of gyrating wave forms but essentially, you're just

writing numbers between minus 1 and 1 into an array which is of a particular

length. So we'll be talking about how to do that

in a moment. So we have our synth.

It's called waveform, and we're writing a waveform into it, which is what makes the

sound. we've got a play head.

Now, the play head, as Matt was describing, is, it's literally the thing

which tells us how many, how many frames there have been.

And we use that to work out whether we should trigger a new beat.

Okay. So we've also got, this array called

notes, which is an integer array. And it holds MIDI notes.

If you know about music, then you'll know what MIDI is.

If you don't really know about music and music technology, you've probably never

heard of it. It's called Musical Instrument Digital

Interface. It's a specification.

For a numbering system that relates to musical notes and musical information.

So these MIDI notes normally what they represent are all the keys on the

keyboard. they're 7-bit numbers, which means that

they go for a range of 0 to 127. There's 128 independent values, the

lower, the number, the lower, The note. So, I'm right down the bottom end of the

piano, as you can see. With all these numbers, zero, zero, zero.

12, 12, 12, whatever. okay.

So, then we've got some float variables. Fc, which is filter cutoff, resonance,

attack, and release. And these are variables which I'm using

to control the filter cutoff resonance, attack and release of my synth.

This is my wave table. Excuse me.

This is my wave table. Its an array and of float variables.

Like I said its going to be between minus one and one and its got four five hundred

and fourteen elements. Now the reason its got 514 elements its

kind of complicated but its because of something called interpolate.

Very briefly what we need to do when we create that way-, when we create a

waveform, is we need to make sure that that waveform can playback at various

different frequencies. So it's sound is made up of lots and lots

of different frequencies and we measure those frequencies in repetitions per

second. Or cycles per second, and the measurement

value we use for that is Hertz. So for example, if I take a sound, a very

small snippet of sound and I repeat it more than 20 times a second we actually

hear it as a pitched note, because it's repeating so fast.

And that's what we think of, we think of music.

Most people just think about pitched notes.

So, in order to be able to have a, a wav form which can be played back at 20

hertz, or at the oth- -- at the other end of the scale 20,000 hertz, which is about

the highest, frequency that we can hear; in fact, I can't hear 20,000 hertz.

What -- who'm I tryin' to kid? As you get older, you can't really hear

up there. I probably can hear about 18,000 hertz

or, if I'm on a good day, with a good wind.

So, in order to be able to do that, to go between a very low frequency sound and a

very high frequency sound, we need to interpolate.

To make the interpolation work, i.e. to make up the numbers that we need.

because that's what interpolation means. It means we're making up numbers that

aren't there. What, because we changed the playback

rate or the waveform, to make up those numbers, we need some spare numbers on

the end. So it's, normally you have a 512 point

buffer, it's called a 512 point buffer because it's, it's, that's the number of

points that you run through to make the sound.

But where you've got a couple of extra points on the end, and we're using those

for interpolation. So that's the reason why it's 514.

Okay, so there are out setup options sorry, they're not our setup options,

they, they are basically our declarations.

We are declaring all the objects that we need in order to make this program work.

and then what I'm doing is I'm going into the setup function.

I'm just declaring a size. I'm creating a, I'm calling new on my

maxim object, and that means I'm setting up my context.

and then I've gone [COUGH] done, done the same thing to my wave form objects.

I'm, I'm creating new synth. So the synth is got a, a waveform in it,

which is waiting to be populated with something with numbers.

And it's also got all the other stuff that we need delays, filters and that

kind of malarkey. Then we're setting up my sliders.

This is the same as the way Marko showed you to do his.

I've got this, which is delayed time that's dt, dg, which is delayed amount or

delayed game. A, which is attack.

R, which is released. F, which is the filter cut off.

And q, which is the filter q, which is the resonance, which is what makes it

sound, sort of acidy. so, there are the sliders that we need.

And then I have another multi-slider, which I'm using to enter the notes.

So you can see here, Mark has explained to you how the multi-slider works.

SEQ is also, that's a sequence. It's a, basically it takes an array.

It takes the array notes. And then it, it fills that array whenever

I interact with the multislider. Okay.

So I then, I'm loading a file which I'm not using.

So actually [SOUND] we don't need that. Frame rate is 30.

the frame rate is roughly the speed of the tick rate.

Just like Matt explained. But instead of running through those

ticks, and using them to trigger drum sounds, although we do that in the more

advanced example. In this example, we're just going to use

it to select A note from our note array and use it to set a frequency for our

waveform generator. Okay.

So, before we do any of that, we're still in Setup.

And you see the section here that I'm highlighting?

This is me generating a waveform. So we know that our buffer is 414 points

long so. We want to fill the array, which is 414

elements long with a bunch of numbers between minus one and one.

[COUGH] Now, I'm going for a sorptive wave here so, I actually want the

waveform to be 512 points, as I've explained, but with a couple of extra

points for good measure. So, what I'm doing is I'm taking the

value, I, and I'm dividing it by 512 to make a value between zero and one.

And then I'm subtracting 0.5 to make a value between negative 0.5 and 0.5.

Now what actually happens when I do that is I, I make a ramp, you know, it's as

if, if you imagine that's my array, the ramp goes up like this, so it's kind of

an inverted sawtooth wave. And as it repeats, it drops down, goes

back to the beginning, goes up again, and this produces a nice harmonic spectrum

that we can filter. It's a very simple waveform, but it

creates all these harmonics And, it pretty much creates every harmonic that

we need. And then, we filter those harmonics out,

and add the resonance for that acid sound.

but the values, the actual amplitude is only for minus, naught .5 to 5.

That's absolutely fine. It's, it's absolutely fine.

We could double it, but then we'd get more distortion.

And you can hear that You know I'd have to do more work balancing this out so

it's just to keep the sound within a reaonable range.

So then I make the, the waveform and then I add it to my synth which is called

ironically enough or confusingly enough waveform.

So I can set the wave table size I could set it to any amount I like that we've

already discussed it's going to be 514. And then I load my wave table.

In. Wave form load wave table wave table.

And then it's wave form dot play. So, that means I've initialized my

synthesiser. I've loaded a wave form.

I can change that at any time, any way that I like.

So you could have 10 different wave forms.

You could have really long wave forms. You could take a picture of your face,

analyze all the pixels, and then use that as a The waveform it's entirely up to you

it's just an array of numbers. So you know be creative and then I'm

pressing play what that really means is it's on.

So ready to rock. In the door method we're doing the same

stuff that Marco explained. We are [COUGH] setting up our sliders

Then we get our slider information in the draw method.

So, if f get, basically if we get something from the frequency slider, we

set the filter that belongs to the wave form object.

and if we get delay time, then we set the delay time.

Yes unless I'm munging I'm dividing it by fifty just to get it into a decent range.

The same thing to delay gang get and to the huge get.

A get and R get. Lot's of good gets.

Because we are in the draw method that's a good place to set the display.

So we display everything. And then we do the business end, which is

ticking through the array, which has the notes in, and using that to set the

frequencies. So, playhead ++, every time we enter the

draw loop, we iterate the playhead. So the tick rate is different to the rate

of actual playback. The tick rate Is quite fast, it's 30

frames a second. We could have 60 or 120.

it can be quite fast. And a tick rate's normally much much

higher than the rate of the rhythm. So what I've done is I've just said,

okay. Well, every four ticks.

We'll say that's a semi quaver, which is a.

Small chunk of a beat, it's a quarter of a beat, so f play had modular four equals

equals zero just the same way Matthews already showed you.

Wave form.ramp, we ramped a [COUGH] knot.5 which is going to be our volume

given the attack time... Yet.

And what that does is it means that, if the attack time's long, it'll be a slow

ramp. And if the attack time, attack time is

fast, it will be a short ramp. And then, following a ramp, we set the

frequency. Wave form set frequency.

Now, we're using this thing, m2f. Now what this does is it takes midi notes

and turns it into frequency information. And this is just looking up an array,

which is a maxim j s here. So it's saying okay, if I get a, a number

zero, that's going to be a midi note of zero.

if I get a number one, a midi note of one, that's going to be a frequency of

8.661957, which we'll never hear. But I generated this with an algorithm.

And I just pasted it in, because it saves you having to worry about it.

Okay? Then we access notes.

We get the play head modulo 4. Sorry, play head divided by 4, modulo 16.

That's basically saying, okay. We've had ticks, that's fine.

But this is the note we actually want. And then we're adding 30, which is a

constant, which is just, so if it was zero, then it would actually be 30.

So finally what we do is the next ti, tick we release.

So immediately we release before we then Retriever.

So if player head module [INAUDIBLE] equals equals one we trigger the release,

and then we're off. There are better ways of doing this, but

not using processing. Okay, so as you can see, we've triggered

our sound, we've set the note for this particular tick and we've released it.

For the following notes, the following tig.

So the next thing to do is to sort out the interaction.

When mouse pressed, what we do is, we just get the user interface stuff, and

that handles all our mouse pressed GUI. Dt mouse pressed, dt mouse pressed, blah.

Same thing in mouse drags so that's useful for mouse devices.

And in mouse release we we just check one thing.

We check to see if the notes have changed in the array that holds all the notes.

And if they have, then we just populate the sequence sorry, we populate the notes

array with the new sequence that's in our sequence similty slider.

And that's what this does, so notes I, which is the current note from 0 to 15,

so there's 16 different steps, we flaw this value basically.

So we get the sequencing value. And then there's a bit of [UNKNOWN] to

make sure that it's the right value and we stick it in there, make, we basically

convert it from the slider value to a mini value.

We could have used the map function to do that, which would have been easier to

read. But instead of using map, I'm just doing

it with standard mathematical operators. Right.

Now that actually is that, is that first test.

So let's just go back and have a look. [MUSIC].

Yeah, that's nice. And here's the delay time again.

[MUSIC]. [SOUND] I wanted to just talk briefly

about the filter because the filter is quite is, I don't know, it's nice to

think about what the filter actually does.

I've already explained that we have a wave form and it goes at a certain rate.

It give us lots of harmonics. And then we use the filter to block them.

But how that process occurs is kind of interesting.

Basically what the filter does [SOUND] is it, it lets everything through [SOUND].

Let's just get a single note [SOUND]. It lets everything through when it's wide

open. [MUSIC] And as we drop it, what it's

actually doing [MUSIC] Is this preventing the weight form from moving very quickly?

The filter basically is averaging smoothing out the weight form/g.

The weight form remember is like that. And it's going really really fast.

Lets say it's going a thousand times a second.

And it's producing all of these harmonics which are.

Two thousand, three thousand, four thousand, five thousand, six thousand,

seven thousand, eight thousand, et cetera, times per second, with an

altitude drop-off. And that's making a very bright sound.

That's making that buzz, that nice, buzzing sound that we, we like.

Well, I'm assuming you like that. If you don't like that [MUSIC].

That then tough, 'cuz that's the sound it makes.

but the thing is that when we repeat it over and over and over again., we're,

actually, when we get to the end of the route, and we drop down again.

That's actually quite a fast move. And that's what creates all the

harmonics. If we smooth that, it prevents the

harmonics from being generated, and it smoothes Filters out that sound, so what

we're actually doing is we're averaging the signal as it goes up, kind of.

and that's fine because it's a slow increase, but then when we get that

sudden drop, we smooth it in the same way we might blur an image.

And that's more or less how we turn high frequencies down.

So, it's really simple and if you're interested in that process.

There's a number of filters that come bundled with the course air package that

we've put together for you. and they run nicely on Android as well,

so you want to have a look at those, they're in the Android package and

there's 4 or 5 of them. And you can actually see the algorithms

if you're interested, you can have a look at them.

Alright, so that's how the synthesiser works.

Now, finally, what I want to do is go back to our,

A more complex example that combines all the bits together and just talk about how

that tinal thing wor, works. Just a few little things that make it a

bit more useable. so I'm going to go back to our music

machine example which is here and I'm going to run it and what's going to

happen is. [MUSIC] It started up straight away

[COUGH] and it's distorting beautifully really not bad.

There's very little I have to do now all of it [MUSIC] Make music.

Let's have some bass drums. I do like a bit of bass drum, can you

hear the bass drum? You can just about, let me knock this one

out. Okay, that's good.

It's quite hard to use that. You could have a nicer keyboard setting

or something like that. [MUSIC] So let's have a look at what

we've done to put the main application together.

So, we've got two synthesizers. now there's a clever way to do this and

there's a stupid way of doing this and just to make your life easier, I've done

it the stupid way. instead of creating an object or a class

which is a synth although I've already done that behind the scenes anyway.

But instead of doing that, just so it's clear and you can see how it's done, I've

just duplicated all of the codes. There was actually two sets.

A brighter, cleverer, more engineering savvy method is to make another class

that encapsulates all of the sliders. And then just to create one of those

objects and to say where you want Where to put it, so that's something we should

have a look at. There's a good example in all of the

current examples that we've given you, there are good examples of classes, and

you should have a look at that those. But I didn't want to do that and find

that no-, that some of you didn't really understand that whole process.

So I've just gone through and I've duplicated all of that code.

So basic stuff is I thought well I want it to look slightly better than it

currently looks so I've created a brushed metal background.

I've positioned all the sliders on the screen and then I've created this brushed

metal background and you see that this is a good tip.

If you can avoid havong to draw Non-animated information.

via algorithmic methods, i.e. if you can avoid having to apply the

interface graphics, do avoid it. Make a Photoshop image that has your

interface. So I've got a slightly embossed area here

and here which these are the panels that hold the information and if I spent more

time on that I can make them look really nice and I've fake knobs and switches

that I copied and pasted of the Internet. Or I could photograph my something from

my set connection and then put those on them instead.

but I guess what I'm trying to say is you can do an awful lot by preparing your

images in Photoshop just like we did last week with the instaspan for the overlay.

It's the same sort of thing. put the effort in there if it's not

going to animate. Put the effort in in Photoshop, make it

look sweet, and then draw it. I must admit I've not really put the

effort in here, but there's a back, there's a basic starting point.

You can see where the panels are; they're sort of lined up.

Another thing you can do is you can put your interactive graphic elements Onto

your screen so that you do that problematically then you screenshot it

the right size and move that into your Photoshop application and then you can

draw on top of it. I guess it's what I'm saying is do the

work in Photoshop is you're not going to have to animate it make it look nice

there. We did exactly did the same thing with

angry droids as well we just Do a bit of support work there.

So that's the basic idea, and you can get away with a lot there.

also it's nice to add custom graphics to your sliders, and you can do that too.

So, we've done that. And then we've loaded it in here.

And then we've done the same thing, exact same thing that Matt did for the drum

track. We created four Boolean arrays.

Track, 1, 2, 3, and 4. These are for our four drum sounds that

were in our drum machine, which is a kick, a snare, a handclap, and a cymbal.

Ideally, I'd have a hi hat. There is a hi hat knocking around in one

of the, folders on the Coursera pack that you've got.

And you can see here, exactly as I said, I just duplicated everything.

So there's the floats that you've already seen.

Except we've added another function, filter attack, which is what gives it

that sort of TB 303 baseline sound. [LAUGH] allegedly.

And then we've got, some transpose functions as well, which allows us to

move it around. We've got a second wave table for the

second object. You can see we've got two syns waveform

and waveform two. And now these are all basically

everything that has a two after it is for the second waveform.

We create a bunch of secondary slide and sliders and multi-sliders to hold all the

separate information and then we load in some samples.

And then we set up a sliders, so we have twice as many sliders.

But they have slightly different numbers in to re, to represent the fact that

they're going to be drawn somewhere else. Now as I said, you would draw them,

screen shot it, import it into Photoshop, do your background, and then just load

the background. Now so we load the background where do I

load the background. Into the bottom of this.

that's the wavetable, exactly the same way as I described in the first example.

Okay the background is loaded, there it is, brushed metal, that's my brushed

metal background. and then here, what I do is I set up the

drum tracks in the same way that Matt's already explained.

I just create these boolean arrays, they're either true or false.

And I set them all to false, so they're all off.

Okay, and then we get all the information in exactly the same way, as we did

before. And then we use the same playHead

information to get the frequency content for both synthesizers.

And then we use another variable, current b, so we could use playHead if we're

using current b too. It doesn't really matter, it's the same.

To find out whether it's if it's true basically, then what we do is [COUGH] we

play that drum sound back. the mass press stuff is exactly the same,

if you click there it sets it And, you've set it to play.

in both mouse press and mouse drags. And other than that, it's exactly the

same as the two examples you've seen. The basic synth example, and the drum

example. And that's how you end up with this.

[MUSIC].

[MUSIC]

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