Beginnner’s Guide to Synthesizers: How They Work and Which to Buy First

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When I was younger I played in a guitar band, there were four of us, a drummer, a bassist and two guitarists. We were ok, but there was nothing that separated us from the 100s of other guitar bands touring at the time. But one day I had a eureka moment, I decided to buy a synth. I didn’t do any research and just bought a Korg MicroKorg because I’d seen another band use one and thought it sounded interesting. The synth arrived and I was instantly baffled by all the knobs, buttons and flashing lights. Confusing words started jumping out at me like ‘oscillator’, ‘modulator’ and ‘arpeggiator’ and loads of other words probably ending in ‘or’. It felt like a futuristic language of the robots or something, needless to say, I was very confused.

We ended up using the synth in just one song, I used one of the default patches which comes pre-installed on the synth. Eventually, I put it in the attic and it sat there collecting dust. A few years later when I started making music again I decided to dig it out and this time learn how to actually use it properly. It wasn’t easy and there wasn’t one simple guide out there on how to play synthesizers for beginners. So I’ve written this article to try and explain as simply as I can, how synthesizers work and therefore allowing you to craft awesome sounds from whichever one you own or chose to own in the future. .

What is a synthesizer?

A synthesizer or synth for short is an electronic musical instrument that produces audio signals. Typically it will consist of an oscillator, a filter, an amplifier, a volume envelope, a filter envelope and a low-frequency oscillator. These components basically fit together to form an electronic circuit which creates and then modifies a sound. Yes, when you strip away the keyboard and flashing lights you soon realize that a synthesizer is actually just a glorified electronics set. .

A brief history of the synthesizer

The synthesizer is one of the most modern instruments in terms of its invention date. With the majority of instruments we know today being adaptations of often centuries old technologies, the synth didn’t appear till much more recently due to the fact it uses electricity, a fairly modern invention in the grand scheme of things.

The actual inventor of the synthesizer is the cause of some debate, and although it didn’t start making an appearance in popular music until the 1960s it can actually trace origin all the way back to 1876!

Unsurprisingly it was an electrical engineer, Elisha Gray, who is thought to have accidentally discovered/ invented a single note oscillator. This lead on to the creation of weird and alien-like creations such as the Theremin. At this stage, the synthesizer was really only capable of producing weird novelty sounds and it wasn’t until the 1930s when polyphonic synthesizers started to be produced in Germany and the USA that people could actually start using these machines to make music.

A theremin from the 1930s…can we really call it an instrument?

Over the next few decades, the synthesizer got refined down, helped greatly with the invention of MIDI. Pioneers such as Harald Bode and later Robert Moog really brought the instruments into the mainstream and the sounds of the synth started appearing on pop music records around the world.

By the 1970s the synthesizer was truly in the mainstream. Portable and affordable models produced by big names such as Yamaha and Roland were finding their synth sounds on many albums.

The synth has continued to evolve ever since and is now a mainstay in most genres of popular music across the globe. .

How do synthesizers produce sound?

Briefly taking you back to the high school science classroom, it is important to remember what ‘sound’ is for a minute.

Sound is essentially a ‘wave’ of energy which travels from a source which creates the wave (via vibration or oscillation) that then travels through the air and to our ears. So a good place to start is to try and imagine every sound you hear more visually.

The picture below crudely illustrates a simple sound wave traveling from source to listener (this is very oversimplified of course but I feel it helps me understand it clearer). The amplitude is essentially the ‘height’ of the wave and equates to what you probably know as the ‘volume’ of the sound. So the harder this Man B hits the triangle the larger the wave would appear.

As you can see I’ve also labeled the wavelength. This is the distance between two peaks on the sound wave. If you imagine the wave traveling at a constant speed from left to right, as the wavelength gets shorter the frequency at which waves reach person B will increase. The frequency translates to what we interpret as the pitch of the sound, so a higher frequency is a higher pitch whilst a a lower frequency would be heard as a lower pitch.

So if person A hits something like a gong the frequency may be much lower and so the sound person B hears will be much lower in pitch. He’s also hit it really hard (is there any other way to hit a gong) and so the amplitude is much higher than before.

So that’s the basics covered. But if that is the case then why doesn’t everything sound identical? How does a piano end up sounding so different to a drum, or a violin so different to a trumpet?

This is because these instruments mentioned are all analog and so don’t just produce a single sound wave but often multiple at once. The difference with creating music using electronics with a synthesizer is that you have a lot more control over the sound produced and this is why a synth is capable of making a huge number of different sounds.

But how are these sounds created in a synth?

As I mentioned a synth is basically a glorified electronic circuit, a sound wave is created and then flows through various components in the circuit which ‘shape’ this sound before it comes out at the end for us to hear.

I want you to think of it as the sound waves journey where it is created and then shaped as it goes through the circuit. This type of synthesis is known as ‘subtractive’ synthesis as the components take away elements of the original sound wave. I will now introduce each of the essential components within that synthesizer circuit.
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Oscillators

Oscillators are pretty important in synthesizers as they are the part of the circuit that generates the sound. But how do oscillators make a sound? Well, the clue is in the name they ‘oscillate’. This oscillation causes electrical vibrations which produce a repeating sound wave. There are many ways of producing sound waves in music, like hitting a drum or strumming a guitar. An oscillator is just another way of doing this using the power of electricity.

Most modern synthesizers will have multiple oscillators. This will allow you to create fuller more interesting sounds.

On top of this, you are also likely to have as sub-oscillator. A sub-oscillator usually plays in an identical key to oscillator one but at a lower pitch, you can usually set how many octaves below oscillator 1 you want this to be. A sub-oscillator is used to ‘beef up’ a sound and make it sound ‘fatter’ and is particularly handy for use in basslines.

There are also low-frequency oscillators in mist synths but I’ll come to that later.

The sound wave produced by the oscillators can have a few different shapes to them or ‘waveforms’. Each one of these different waveforms will sound different to the human ear. There are 4 common waveform types that you are most likely to come across when you start learning to play synthesizer, sine, square, triangle and sawtooth. Synths will also often have some other waveforms perhaps unique to that synth.

We can handily visualize these waveforms on what is known as an oscilloscope, hopefully making it easier for you to understand the sound rather than trying to picture it in your head.

Synth Waveforms Explained

Sine Waves

The sinusoidal or ‘sine’ wave is the ‘classic’ or ‘pure’ sound wave, the one that gets shown in all physics textbooks when the physics of sound is described, and the one used in the terrible drawings of stick men above.

In terms of playing the synth, it is probably the waveform you will use the least regularly as it is tricky to get it to sound interesting.

A tuning fork gives out a nice example of a sine wave, a constant note at one single frequency. Boring and not great as part of a musical composition.

Square Waves

Square waves unsurprisingly have a square look to them. They have a video game type sound, nowhere near as smooth sounding as a sine wave. In fact, it is probably best to think of them as opposites in terms of how they will sound.

Due to its square nature, a square wave covers a series of harmonics. This gives this waveform a ‘richer’ sound.

Triangle Wave

I hope it makes sense from looking at a triangle wave that it sounds about halfway between a square wave and a sine wave. They are similar to square waves in the fact they cover more than one harmonic.

Sawtooth Wave

Again, as with the square and triangle waves, a sawtooth wave is named after what it looks like, in this case the tooth of a saw. If you listen to a sawtooth wave it will probably sound familiar as it is a very popular waveform in music.

Sawtooth waves are known for a distinct buzzing sound.
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Filters

Voltage controlled filters (VCFs) on a synth are there to filter out certain frequencies from the sound.

It is important to remember that when you are playing just a single note on a synth, just as with most other instruments you aren’t simply hearing the route notes but a whole variety of harmonics of that note at different frequencies across the spectrum. By applying a filter you are eliminating some of these frequencies, focussing down more and more on a certain part of the broad frequency spectrum.

High and low pass filters

There are two types of filter on most synths. A high pass filter and a low pass filter. Maybe you don’t want very high frequencies if you are trying to create a bass sound for example.

You may or may not be familiar with the idea of EQ in music. I wrote a whole article about it here. But in summary, it is the process of boosting or reducing certain frequencies of a sound. In a parametric EQ you can do this for very specific frequencies or you can change whole ranges of frequencies at once. The image below shows an EQ where frequencies within a very specific range have been filtered out (amplitude is on the y-axis and frequency is on the x-axis).

A filter works like a very simple EQ which allows through only frequencies above or below a specific frequency known as the ‘cutoff’.

A high pass filter will let high frequencies pass (I told you this synth jargon was simple really) so when you turn on this filter you will stop hearing lower frequencies. Likewise, if you want to get rid of high frequencies you can use a low pass filter to only allow bass frequencies through.

You may now be beginning to understand why this process is called ‘subtractive synthesis’ we are taking the original sound wave produced by the oscillator and then manipulating it to shape the sound how we desire.

There are a few other terms associated with filters that you may come across on your synth:

Cutoff

The cutoff frequency is the frequency at which the filter begins to work.

A filter doesn’t usually act as a wall, abruptly cutting out all frequencies above or below a certain point, but rather starts applying at a cutoff point and then slopes off from there. The rate at which this happens can be changed on many synths and is known as the slope.

Slope

The slope can usually be changed between -12db and -24db which is ‘decibels per octave’. With -24db being the steeper slope.

Resonance

A filter on it’s own won’t really shape your sound into something that interesting. However, most synths come with some other settings within the filter that will help you make some much more interesting music.

Filter resonance adds a peak at the point of the cutoff point; routing sounds back into the filter resulting ultimately in feedback. Resonance will, therefore, give you some quite harsh sounds but also some brighter sounds too. It’s a fine line between awesome and painful but very fun to experiment with.

Most synths will let you modulate the filter which is when you get some really interesting sounds. But before I try and explain how the modulation works I think it is best if I explain the final part of the main synthesizer circuit which is the amplifier:
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The Amplifier

Continuing on its journey once your sound wave has passed through a filter it will reach the voltage controlled amplifier (VCA). Where the signal will be amplified in order for us to hear.

Within the amplifier is what is known as the ASDR envelope and this is the final change you get to manipulate the sound before it leaves the synth. You are manipulating to volume of the sound in the amplifier.

ADSR Envelopes

Amp Envelope

ADSR stands for Attack, Decay, Sustain and Release.

I find the concept of ADSR is best visualized as a graph. Each note or chord you play will produce a graph looking something like the one shown below. Time runs along the bottom axis, the left corner being where you first press the key (if you are using a keyboard) and then amplitude/ volume is shown on the y-axis up the side.

Attack

The attack is the amount of time it takes for a note to reach peak amplitude (volume). Strumming a guitar or hitting a drum are examples of an extremely quick attack. The loudest part of the note or chord happens almost instantly.

In contrast, other instruments like strings or a synth pad sound will have a slower attack taking time to reach the peak amplitude.

Decay

The decay is the amount of time that note takes to go from the peak amplitude to the ‘sustain’ level (see below).

If you simply want short punchy notes that have a loud peak but then quickly dip back down then set a faster decay time. But if you want that peak to be present for longer extend the decay time.

Sustain

Unlike attack and decay, sustain isn’t a measure of time but is a measure of amplitude. On a synthesizer, this sustained level lasts for as long as you hold the note down, which could be forever (if you have that much time on your hands).

Release

And finally, the release is the amount of time it takes once you let go of the note for the amplitude to return to zero (silence).
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Modulation

So the basic construction of a synthesizer is fairly simple. You have your oscillators producing a sound, a filter letting through certain frequencies of that sound and then an amplifier converting that to an audible signal.

But with just those capabilities a synth would be quite limited. You would be able to produce the basic waveform sounds and take away certain frequencies, but that would be it a bit boring. So to create more weird and wonderful sounds we look to modulation.

Modulation is required within a synt

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