- What is a synthesizer?
- A brief history of the synthesizer
- How do synthesizers produce sound?
- Synth waveforms explained
- ADSR envelopes
- Envelope modulation
- What is the difference between additive and subtractive synthesis
- What is modular synthesis
- Buying your first synth
- Hardware vs software synth
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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.
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.
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.
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
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 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.
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.
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.
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:
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.
The slope can usually be changed between -12db and -24db which is ‘decibels per octave’. With -24db being the steeper slope.
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:
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 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.
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.
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.
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).
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 synthesizer in order to change (modulate) the sound of a note. Modulation comes in several forms (which I’ll explain below) but it basically always works by increasing or decreasing the level of a particular element.
Each type of modulation has a source and a destination, with the source being the thing that creates the modulation and then the destination being the thing that is being modulated.
The destinations (things that can be modulated) are pitch, cutoff frequency, and volume. The source (of the modulation) can come in two types either one that varies over the length of the note i.e an envelope (as mentioned above) or a low-frequency oscillator, or as one that affects the entire note such as pitch or velocity.
Filter Modulation Envelope
On most synths, there will be a dial which you use to set the amount/ depth of modulation on the filter. This modulates the cutoff frequency either up or down.
The ADSR envelope then defines how quickly this modulation occurs (attack), how quickly it gets to the sustain filter level and then once you release the note how long it takes for the filter to return to the original cutoff frequency.
So the two ADSR envelopes are working at the same time which is very tricky to imagine in your head, so don’t worry if you don’t get it straight away.
And they have to work together. There is no point in having a gradual attack and slow release on the filter envelope when you have a fast attack and fast release on the amp envelope. The note will have finished before the filter envelope has a chance to do anything.
Low-Frequency Oscillators (LFOs)
You hopefully know what an oscillator is now after reading the earlier section of this article. Well, on top of your regular oscillator(s) and your sub-oscillator you are also very likely to have what is known as a ‘low-frequency oscillator’ (LFO).
As with the other oscillators, the LFO can have a variety of different waveforms, sine, triangle, sawtooth, square etc. The difference with an LFO is that it isn’t used as an audible signal but is used to ‘modulate’ another aspect of the sound. The LFO is technically producing a sound but it is usually below 20Hz and so is inaudible to most humans unless you have supernatural hearing.
So you can use this LFO to modulate the pitch, the filter or the volume of the sound. You can then change the various settings on the LFO such as:
You can change the speed or rate of the LFO using a dial. Which is how long it takes to move through a certain period of the waveform.
On many synthesizers, you will also have a knob or wheel to dial in the depth of the LFO. This is the amount the LFO modulates the sound, with depth set to full the LFO will affect the sound quite significantly whilst when the depth is set at the lowest point it will barely be noticeable.
An arpeggiator (sometimes reffered to as an ‘arp’) in it’s simplest form is a function built into many synths that automatically turns notes on and off. But really the purpose of an arpeggiator is to allow the player to make their synth play a series of notes one after another, in a sequence, without having to press each individual note every time. A very handy function if you don’t have much piano playing experience!
Most synthesizers with arpeggiators will have different types to choose from. These may include ‘up’ where notes rise upwards from the base note, ‘UpDown’ where the sequence goes up and then back down and even ‘Random’ where notes will be played in a random order. Have a mess around with the settings on your particular synthesizer and see what happens.
The tempo is the speed at which the arpeggiation (is that a word?) takes place. A fast tempo ‘Up’ arpeggiator will rise up the sequence much faster than a low tempo one. This will most likely be displayed in beats per minute (BPM) and it will often make logical sense to have this set to the same BPM as the rest of your song so it fits nicely.
A handy function on an arpeggiator is the latch function. This means the sequence of notes will continue to play without you having to hold the note or notes down continuously. This then allows you to mess around with other features such as filters whilst the notes continue to play as if by magic.
What is the difference between Additive and Subtractive Synthesis?
What I have spoken about above is subtractive synthesis, this is the synthesis you are most likely to come across. But you may hear about another type of synthesis and that is additive synthesis.
Instead of offering a variety of different waveforms, an additive synth only tends to produce sine waves. These sine waves from multiple oscillators can then be combined to build different sounds. This is done by tuning each oscillator to a frequency corresponding to a certain harmonic. For this reason, additive synthesizers tend to have more oscillators to be able to build up a complex sound.
What is a Modular Synthesizer?
You may be familiar with the look of modular synthesizers as instruments that look like they belong in a spaceship.
A modular synth differs from the perhaps more familiar keyboard synthesizers in the fact that instead of having components already wired together in a fixed order (i.e oscillators to filters to an amplifier), you have the ability to vary the signal path however you want.
The reason it is called a ‘modular’ synth comes from the fact it is built up from separate ‘modules’. Each module is a self-contained component that forms part of the overall system, for example, you could have an LFO module or a filter module etc. You are basically just constructing a big electronic circuit. These modules are connected to one another via small cables known as ‘patch cables’.
You are hopefully now familiar with the basic elements and how they combine and a modular synth works in much the same way with modules divided into three broad categories:
These are the sound generators, noise generators, LFOs and envelope generators.
Where the source sounds are shaped, filters, volume and various other effects.
These are elements such as clocks or gates which trigger other elements.
The weird thing about a modular synthesizer is that you rarely see one with a keyboard (ignore the above picture). It is possible to hook up a keyboard to a modular synth but most of the time players will just control the voltage which will then alter the sound.
That is essentially what a keyboard is doing in a keyboard synth. It is sending a signal of a particular voltage to the oscillators. This varying voltage is what determines the pitch of the oscillator. For every volt you add, you go up an octave in the scale. So to play different notes in a modular synth you just change the voltage going to the oscillator.
You can also control voltage going between other modules on the modular synth. Each module will tend to have an input and output but also a ‘control voltage’ setting. By altering the voltage going between different components in the synth you can shape the sound and the possibilities are limitless.
Modular synthesis is definitely not something for the faint-hearted and I fully recommend you get to grip with the basics to start with before spending a lot of money on modules which may cause a lot of confusion at first.
Buying your first synth
You should now have a pretty good idea of how synths work and this is vital. I didn’t bother learning the basics and bought a couple early on in my music career thinking “how hard can it be?”….well it turns out it can be quite confusing if you don’t know the basic concepts I’ve talked about in this article. I ended up just using the presets or twiddling knobs until it sounded good.
And I’m not against this method of twiddling and pressing buttons, it is a fun way to find new sounds. But it is extremely frustrating when you create something and have no idea how you did it, it’s much more satisfying to know exactly how you shaped such an awesome sound.
Reading about the concepts of synthesis can be very confusing if you don’t have a synth in front of you to make the elements feel tangible. Therefore I recommend getting hold of a synth as soon as you can to practice using all the elements and it will then hopefully become fully clear in your mind.
Hardware vs Software Synth?
A software synthesizer is a software program that can be downloaded onto your computer that imitates a traditional synthesizer.
If you aren’t sure whether synthesis is for you, then start with a software synth. It doesn’t matter if it doesn’t sound as authentic as a hardware synth (although many do these days), it is simply to be used for practice and learning the basics.
The great thing is you can get software versions of some classic synths, that if you were to buy the physical versions of, could set you back 1000s of dollars! It is a great way to mess around without worrying about investing in something you may not like or use. That said, don’t download a software version of a really complex modular synth when you first begin as this will make you angry and confused. Start simple and master the basics first.
Once you have got to grips with that, I recommend getting hold of a lower end hardware synthesizer. There is just something more fun about having the physical instrument there, the electronics physically working in real time as you turn the knobs and press the buttons rather than using a software synth that is just pretending. There are plenty of great options out there that won’t break the bank.
I love vintage synths and think everyone should own one eventually. But as a beginner, I would recommend buying yourself a more modern new analog synth to start with. If you buy a vintage synth off of eBay when you don’t really know what you are doing there are lots of things that could go wrong. Where do you go if a component breaks? How do you know that it sounds exactly as it should? How do you know the price you paid was reasonable?
For my recommendations on synths for the beginner check out the recommended products page here.
Once you get to grips with your first synth, I’m sure you will have no problem filling your home studio with hundreds of vintage synths.