The synthesizer is now an essential part of today’s modern studio, and any aspiring music producer should be able to answer the question, how do synthesizers work? Understanding how they work will open up a whole world of sound creation and manipulation that can transform your recordings and productions. It’s one of my favorite instruments in the studio.
What is a synthesizer? A synth (sometimes seen as synthesiser) is an electronic instrument that can create a wide range of different sounds and textures. A synth can imitate real instruments, or can be used to create new sounds that have never been heard before.
Synths can come in both hardware and software versions. You can now find software emulation plugins of the most famous and well-known hardware synths from years gone by. This can help modern-day producers to achieve those classic synth sounds at the fraction of the cost of the original models.
Where Did The Synthesizer Come From?
The history of the synth can be a long and complicated story. The story can also depend on what sort of electronic music device is actually classified as a synthesizer.
The Telharmonium and theremin had become the first electronic instruments in the late 19th and early 20th centuries. Many other types of electronic instrument had been created as well in the following decades. But in 1956 the word “synthesizer” first appeared, with the Electronic Music Synthesizer Mark I from the American company RCA.
The first synth to be available to the public was the 900 Series Modular Systems synthesizer from Robert Moog – although these early synths could cost more than a house. Then, in 1970, came the Minimoog, a smaller and compact version of Moog’s earlier synth that was more easily available to the musicians of the day.
The Minimoog changed the landscape for the synthesizer as a proper instrument, and all advances in the technology of the synth can be traced back to this instrument.
The actual notes produced by most synths are controlled by keyboards. The tonal qualities of the sounds are controlled by all of the knobs, buttons and sliders found on the synth’s control panel. Most synth parameters can now be controlled through MIDI as well, helping producers create more dynamic sounds that can change shape and texture over time.
Below is a picture of a Minimoog that shows a typical layout for a hardware device – this design was released in 1970 as a smaller compact version of the famous Moog modular synth that was first released in the mid 1960s. The Minimoog was relaunched in 2002 as the Minimoog Voyager.
It’s a classic model and design, and one of my favorite instruments to play.
How Do Synthesizers Work – Synthesizer Building Blocks
You’ll find that the controls on a synth, whether hardware or software, are mainly based around the same principles of audio synthesis.
- Oscillators (VCO): generate the raw sound later shaped by other controls. Most synths have 1, 2, or 3 oscillators, with each one able to produce different sounds depending on the shape of the wave used – the common wave types are sine, square, triangle, and sawtooth. The sounds of each oscillator can then be combined.
- Filters (VCF): these can come in a few varieties – hi-pass, lo-pass, bandpass, or notch. The filter removes frequencies from the sound – the frequency where the filter effect takes place is called the cutoff frequency. The ‘Q‘ value can emphasise this selected frequency by making it resonate, helping to produce a unique sound.
- Amplifier (VCA): boosts the signal to alter the sound’s volume.
- Envelope: ‘shapes‘ the sound using parameters called attack, decay, sustain, and release – this is why they are known as ADSR envelopes.
The key on the keyboard is pressed – the attack is the time it takes the sound to reach it’s full volume. The decay is the time it takes this maximum volume to fall to the volume set by the sustain.
The sustain is the volume level of the sound during the time the key is pressed. The release is the time it takes the volume to reach zero once the key has been released.
The LFO and the Arpeggiator
- LFO: Low Frequency Oscillator. This oscillator doesn’t produce sound like the VCO, but is used to directly affect the sound generated by the synth, with a frequency usually below 20 Hz.
The LFO can be assigned to affect different parts of the sound. For example, it can create rhythmic effects such as vibrato by oscillating the amplifier, or create filter sweeps by oscillating the filter cutoff frequency.
- Arpeggiator: this section of a synth can create a repeating sequence of notes, often heard in techno and house music. You can control aspects like the speed, the notes, the octave range, and the order of the notes. These are usually synchronized to the beat as well, creating exciting dance music patterns.
Here’s how you create a sound using a synthesizer:
- The oscillator produces the sound (you can use one oscillator or combine several together)
- The filter removes certain frequencies from the sound
- The ADSR envelope shapes the sound
- The LFO can be applied to any of the above three stages, helping to produce wildly different sounds
When it comes to answering the question we started with – how do synthesizers work – you need to know about the different types of oscillator waveshapes.
You may be wondering how each waveform produces it’s characteristic sound. Each waveform has it’s own unique mixture of a fundamental frequency along with harmonic frequencies (or overtones). And each harmonic frequency is a simple multiple of the fundamental frequency.
For example, if the fundamental frequency is 220 Hz (the note ‘A’), then the first harmonic would be at 440 Hz, the third at 660 Hz, and so on. The balance of the fundamental frequency and the different harmonic frequencies is what gives each different waveform it’s unique sound.
- Sine Wave: the purest sound waveform out of the four, with no harmonics involved at all. Sine waves form the basis of all other waveforms
- Square Wave: these waveforms contain harmonics, contributing to the square shape
- Sawtooth Wave: the sawtooth wave has the highest harmonic content amongst the four types of wave
- Triangle Wave: similar to the square wave, but the harmonics in the triangle wave are less powerful
Different Types of Synthesis
These days you’ll see lots of different types of synthesizer in the shops and online. The main forms to be aware of are:
- Subtractive Synthesis: the raw sound is created by the oscillator, the filters remove selected parts of the sound, and the amplifier boosts the signal. The amplifier is controlled by the ADSR envelope. Other aspects like the LFO, along with endless ways to route signals to different modules, helps to create the infinite number of sounds you can get from this type of synthesis.
- Additive Synthesis: the opposite to subtractive synthesis – instead of filtering away parts of the oscillator waveforms, additive synthesis builds sounds by adding together waveforms.
- FM Synthesis: this is Frequency Modulation synthesis. The signal generators are known as ‘operators’ (instead of oscillators). One operator will be used as a base signal, and the other operator will be used to modulate and modify the base signal. However, a synth can have more than just two operators. The more you add together, the more complex the sound can become. You can also have other modulators as well, like filters and envelopes.
- Sample-Based/Granular Synthesis: this type of synthesis is usually software-based. Tiny fragments of a sample are triggered by the software when you play a note. The note is held when these tiny samples are continually looped by the software.
The pitch of the sample results from the software playing the sample back at different speeds. You’ll also have the other usual methods of modulating the sound as well – filters, envelopes, and amplifiers among them. You can create amazing sound-beds and textures with this kind of synthesis, and it’s very popular in the film-scoring world.
One of the modular synths that was first commercially available to musicians and producers was the famous Moog instrument in 1965. ‘Modules‘ could be bought separately and then connected together – this allowed modular synthesis systems to be built up over time, as the modules were very expensive to buy.
Some of the modules available were:
- VCO – Voltage-Controlled Oscillator
- LFO – Low-Frequency Oscillator
- ADSR envelope – Attack/Sustain/Decay/Release
- VCF – Voltage-Controlled Filter
- VCA – Voltage-Controlled Amplifier
- Ring Modulator – when you hear that well-known robotic or metallic sound, then that’s a ring modulator at work
- Mixer – this combines all the various signals from the other modules in the synthesizer
- Sequencer – these modules can create patterns of notes and sounds. Below is a video of some of the sequencer options found on the Arturia MicroBrute synth ->
Modular synths have made a massive comeback over recent years. These modules are available from lots of different synth makers from all over the world.
I definitely think it’s worth learning about the different parts of the synthesizer so you can answer that all-important question – how do synthesizers work? You will find it becomes much easier to get stuck into creating new and exciting synth sounds for your music productions. Coming up with these new sounds can be fun and can inspire whole new directions for your music.
The synthesizer is one of the most important and influential instruments used in music creation, and if you can learn how to use them then you’ll be one step closer to creating amazing productions.