Name: Code-It-Yourself! Sound Synthesizer #3 - Instruments & Polyphony
Uploaded: 2020-03-28T17:12:11.000Z
Duration: 24 min 15 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Reflexive pronouns

Welcome to part three of my coat yourself.

Siri's the music you could hear playing in the background.

It's the marble machine I went to go synthesized by the sound synthesizer that many Not only is is a wonderful melody, but it highlights the three things we're gonna talk about.

This video first is looking at a frequency modulation, which is very important for giving a real texture to the sound.

This is ever so subtly changing frequency.

No, lost its play for the second part will be looking at voices and instruments.

Can we come up with a nice data structure that wraps up everything we've done so far?

So the oscillators on the envelopes to represent a particularly on finally, at long last will be looking at polyphony for Paul, if only depending on this is the ability to play multiple notes at the same time.

I'm starting with the code that we used at the end of the last video, and if you remember, this code really just contains a simple oscillator on an envelope on.

All of the good stuff happens in this make noise function here.

Let's have a listen so far, Very nice so we can hear the envelope.

Theo, we're going to be looking at frequency modulation.

There is a significant amount of maths behind the theory of frequency modulation.

I'm not going to go into the full derivation of the formula.

It's not really the scope of this video, but we'll take one that's ready made, and I'll try and explain bits of it.

The purpose of frequency modulation, though, is to add a little bit of vibrato to the sound, and this can have a lot of depth and character and texture to the tones that we can hear.

Whereas I would usually talk through the theory and then write the code, I'm going to do it the other way around this time so we can listen to the effect first.

That might make explaining the maths a little simpler, so I'm going to make some modifications to oscillator function.

For now, I'm just going to hard code in the frequency modulation code.

One hurts wave to modulate the note that I'm playing and what we should hear is a siren like sound way.

And if I choose a different note, the overall pitch of the siren is a different frequency.

If I increase the frequency of our base signal here, you could say it's twice as quick now e.

That's because I've reduced the amplitude.

Sirens are typically considered an instrument, so let's try and make it sound a little nicer.

Effective frequency modulation is very subtle.

So I want the amplitude to be quite low and I'm going to change the frequency to about five.

Let's have a listen so you can definitely hear that fight.

The blue one at the top will be unnoticed.

You could say I can change the frequency on the slide ahead on DTH e sound wave At the bottom is our low frequency.

This is Ah in frequency modulation parlance.

The top one is called our carrier frequency on dth e bottom one is our message appear I've entered the formula for frequency modulation.

Let's enable it to see what the way form looks like and we can see when the two way forms are modulated.

We see a clustering off low frequencies, followed by high frequencies and low frequencies and high frequencies.

And so if I very gently changed the low frequency, we can see the clusters get tighter and tighter.

And if I change the higher frequency, which will be the note we can see, that's also changes the output wave form.

We can change the effect that the low frequency has on the fight high frequency by altering its amplitude on that, I call this a fudge factor, but this is actually quite a complex phenomenon in the frequency modulation equation.

So if I reduce the amplitude, we can see we've just left with the original note on.

As I increase this value, we see that the frequency modulation becomes more prominent and he could do interesting things with this.

In fact, if I turn it right up, we start getting very interesting way forms.

Let's go back to our very first oscillator equation on what's considered the low frequency oscillator part first so we would have low frequency oscillators amplitude sign off the frequency that we want Times t.

Now, if you remember from our earlier videos, when you want to mix frequencies together, you add them.

So we also need the frequency of our note times t on.

We add them together, and that gives us our overall frequency, which then we can pass into another sign equation to give us output results.

Keen mathematicians out there may have spotted something a bit odd about left in the use of tea.

I don't want this to be a video about mathematics.

And if you're really interested, there are many resources online that talk about how frequency modulation is really a combination off triggered a metric identities on calculus.

Suffice to say, the equation will end with the end is a bit of a body approximation.

What is good enough for the purposes of this video?

I'm now going to modify our oscillator function so it always uses a low frequency oscillator.

So I've included here the frequency on DTH e amplitude, but I'm giving them default values in case we don't want to use it on.

I'm going to create a base frequency so we can use this frequency and the other types of oscillators.

And so a sine wave simply becomes the sign.

The frequency now the only one that's tricky to modify.

Here is the digital approximation to a sore wave because it doesn't use D frequency, and it works in real time and doesn't use angular velocity.

That said, the translation from Hertz In real time too angular velocity is trivial.

And I prefer the analog cell too late anyway.

So his original Slater function We'll just play it and make sure it still looks nice.

But now we've got some additional arguments we can pass in s so the first thing is our frequency.

So let's set that to five hertz, and we'll set our amplitude to be quite small, maybe too small.

Let's see what the square wave sounds like.

I like that Now that we've got envelopes oscillators, low frequency oscillators and frequency modulation, we can have a crack it trying to create realistic sounding instruments.

I'm going to try and make a harmonica type sound like you heard at the start of this video in the audio track by Winter Gun.

I know a harmonica is a reed instrument, and it's a breathe the reed instrument.

So for Reed, you typically want square waves on for breathing sounds.

You want noise, Remember, for noise oscillators.

It doesn't matter what the frequency is going to be.

I was going to put zero de time passed that in on dth.

Well, that doesn't sound anything like a harmonica.

There we go, going to add in just a load of noise and a DC offset intothe.

Now it does almost sound like a harmonica.