Working With Synthesizers - Part III

Part three: Different types of synthesis – Subtractive, Additive and FM

In this article series we are going to have a look at synthesizers! We will start with the very basic knowledge and use it then to understand complex sound design, unique workflows and different types of synthesis. 

Subtractive Synthesis

Perhaps the most well-known form of sound synthesis is subtractive Synthesis. The word subtractive describes the process of cutting away harmonics from the signal. Why would we do that? 

The point of subtractive synthesis is to have Oscillators with waveforms that typically are rich in overtones, such as saw or square. With one or several filters we are able to take away some of those overtones again, to shape the sound and its timbre the way we want them to be. Envelopes and LFOs are of great help here, for they can modulate the filter and get the sound moving. With several Oscillators tuned to different octaves and semitones or being slightly detuned subtractive synthesis works well for making huge leads, bass sounds … and actually almost anything. It is only limited by the waveforms it can use, which mostly are Square, Saw, Triangle and Sine. 

The list of examples is endless – some of the most common subtractive Synthesizers are Moog Minimoog, u-he Diva, Arturia Pigments Analog Section and many more … 


Additive Synthesis 

This type of sound synthesis is one of the most fundamental one, as it is based on the general idea that every signal, no matter how complex it is, can be formed out of several single sine waves. (Remember: Sine waves have no overtones; they consist of one fundamental frequency only!) 

Additive Synthesis works in exactly that way: You can put together a bunch of sine waves to make a sound. Those mostly result in a bell like timbre, also works well for (dissonant) drones and pads and is generally used quiet often to imitate the sounds of real instruments. 

Modern synthesizers with additive synthesis often have come up with ways to work with those sine waves (often called particles), in which you don’t have to add every particle manually but instead have parameters to control them in various ways. Check out the latest version of Pigments 3 by Arturia for that: The harmonic engine is exactly that and is a lot of fun! 

If you want to try adding your very own particles together, check out Ableton’s Operator. It is an FM Synthesizer but also features additive synthesis. Just use the A Oscillator, choose a Sine Wave and then start painting your harmonics with the blue stripes. For sure there’s also a lot more synthesizers that can do additive synthesis, such as Native Instrument Razor. 


FM (Frequency Modulation) Synthesis 

Undeniably my favorite type of synthesis – taking the sine waves one step further now with FM Synthesis! This time we are using several oscillators to modulate each other. Remember saying LFOs are just oscillators to slow for the audible spectrum and therefor can modulate stuff well? Now we are using audible oscillators to modulate … oscillators. Ableton’s Operator is a perfect FM Synthesizer – it features four oscillators with several waveforms but trust me, using sine waves is already fun enough in the beginning! Playing around with the Amplitude Envelopes of each oscillator will change the timbre of the sound interestingly: Imagine Oscillator A being a sine wave at 440 Hz and a long sustain and release phase in the amplitude and Oscillator B being a sine wave at 880 Hz, with no sustain and release at all, just 100 ms Decay. The signal will be richer in overtones only for 100 ms and then go back to the original 440 Hz sine, almost like having a filter with this envelope. 

Layering several Oscillators together will result in very complex sounds. FM can be used for almost anything and it’s great for adding a unique timbre to your sound! You could find yourself experimenting with different settings for hours though … Check out Korg Opsix, Ableton Operator, Native Instrument FM8, x-fer Serum, … 


In the next article we will talk about more types of synthesis, like Wavetable and Granular!

written by Kos:mo for weltsound.