An Introduction To Sound Synthesis

Nico
Nico
Aug 9, 2017 · 6 min read
Photo by Marc Mueller

Chances are, you like electronic music. If you don’t: that’s not a problem.

Nevertheless, a lot of new songs contain pure digitally created sounds.

But let’s be honest, you don’t really pay attention to that, right? Well, producers, like myself, do. We can’t help but listen to every little sound in a song and think about how it was made.

Listening to songs and understanding what went into creating such a piece, significantly adds to the experience.

This article is here for you to understand how pure electronic sounds are being made, allowing you to enjoy and appreciate music even more.

||Disclaimer: When listening to the demos on phone speakers, the sound tends to distort. Try headphones maybe. :)

So, let’s start with an easy example:

Drake’s ‘Redemption’

For this article I’d like to refer to Drake’s song ‘Redemption’. Take a listen to the first 10 seconds of the song:

Notice that warm, slow sound in the intro? That’s called a ‘pad’.

Hang in for another 4 minutes and at the end of this article, you will know exactly how this sound was made.

Synthesis

The process of making digital sounds is called synthesis. Surprisingly, devices that synthesize are called synthesizers.

When you read that word, you probably think of something like this:

Photo by Marc Mueller

But synthesizers don’t have to be analog, they can also be digital. There are many different software synthesizers and they come with different features and characteristics, but generally speaking, they all work on a similar basis.

Arguably the best software synthesizer that money can buy right now is Xfer’s ‘Serum’, it looks like this:

Xfer Serum

At first sight, it may look rather intimidating, but luckily I’m here for you to explain it.

Oscillators

Oscillators are the things that create the sound. In ‘Serum’, there are 3 of them:

  • 2 Wavetable Oscillators
  • 1 Sub Oscillator

For the start, let’s focus on the 2 wavetable oscillators. One of them looks like this:

A Wavetable Oscillator in Serum

The green squiggly line is a waveform.

||Waveforms are basically just a graph of sound pressure against time.

This oscillator creates sound through looping this waveform at a particular frequency. The timbre of the sound gets defined by the shape of the waveform.

There are unlimited waveforms, but only a few basic ones that you need to know.

  1. Sinusoidal Waves

This waveform is the most basic one of all, as it consists of only one harmonic. It looks like this:

A Sine Wave

You might be wondering how it sounds…

Well, it doesn’t sound too pretty, I have to admit, but this is exactly what was used to create the pad in Drake’s Redemption.

When played in a chord, meaning that multiple sine waves are played at different pitches, it already sounds relatively close to Drake’s pad.

Now, let’s get a little more complicated.

2. Sawtooth Waves

Saw waves have harmonics. This means that the sound is a lot more complex and spans across a wider frequency range. The saw wave looks like this:

A Saw Wave

And sounds like this:

Saw waves can be found in 90% of all electronic songs. This wave is very versatile and sounds great when played in a chord. That’s pretty much all you need to know for now.

3. Square Wave

Square waves are a lot more complex and there’s a lot to talk about, but for this article I just want you to understand how it looks like and how it sounds. Here’s it’s waveform:

and here’s what it sounds like:

But what about wavetables?

What makes an oscillator a wavetable one, is it’s ability to store multiple waveforms and morph through them. This means that you can change the timbre of the sound over time, allowing you to create more complex sounds.

When more than one wavetable is stored in the oscillator, it looks like this:

A Wavetable

Pretty, right?

So, let’s take the next step.

Filters

These are used to ‘carve out’ frequencies of your generated sound. There are many different types of filters and they all affect different frequencies ranges.

The most basic one is a ‘Low Pass Filter’. As the name suggests, this filter filters out high frequencies and passes low ones. Therefore, it’s shape looks like this:

A Low Pass Filter

Here, the little bump in the filter curve is called the ‘resonance’. This point marks the cutoff frequency at which the high frequencies are slowly being ‘cut off’.

The opposite of such filter would be called a ‘High Pass Filter’, which would cut the low frequencies, while keeping the high ones.

Filtering a square wave sounds kind of cool, so take a listen:

Wait.. How did I make the filter move over time though?

Here’s the answer:

Modulation

Modulation is the process of controlling a parameter inside the synthesizer, essentially by using one of two sources:

  • LFOs
  • Envelopes

LFO stands for ‘Low Frequency Oscillator’. As the name suggests, these are oscillators that oscillate at very low frequencies. Their signal cannot be heard, but instead is being used to modulate a parameter in the synthesizer. The shape of an LFO can be widely customized, however in this example it looks like this:

An LFO

The blue lines dictate the LFOs shape. In our example of a pad, this LFO shape is being looped at a frequency of 2.8Hz and assigned to modulate the pitch of our sine oscillator. Simply put, the pitch (or frequency) of our sine wave gets increased and decreased 2.8 times per second.

In our pad, the modulation is very subtle, but vital for the sound.

It now sounds like this:

However, at the start of the sound, there is a slow glide up in frequency. This one-time event, at the start of each note, can be achieved by using an envelope.

Envelopes also modulate parameters, but only once. If you want the envelope to modulate the sound again, you have to either play another note or play the same note again.

Envelopes inside Serum look like this:

An Envelope

Here we can see that the currently selected envelope (Env 3) quickly drops with a decay of 491ms and never repeats.

So, let’s assign this envelope to the pitch of the sine oscillator as well, but inversely, meaning that the pitch quickly rises.

This gives us a sound like this:

Now, after applying a few effects, we got a final pad which sounds like this:

However, there is no guarantee that Drake’s producer made this pad like I did. In fact, he might have also used an analog synthesizer. We simply don’t know. But what we do know, is that this sound is very basic and only scratches the surface of sound synthesis. I hope that you can now look at the synthesizer from above and at least understand the different sections of it. There’s a lot more to synthesis than I explained in this article and I am more than happy to cover that as well in a different post.

Feel free to suggest new topics and give your opinion on this text!

-Nico

Nico

Written by

Nico

Musician, Geek, Designer and aspiring cook. soundcloud.com/thatnick

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