4 Main types of Synthesis explained: Wavetable, Subtractive, Additive, and FM

Are you new to synths like Massive, Serum or Ableton´s Wavetable?

Today with Top Music Arts, we bring you a quick guide about the 4 main types of Sound Synthesis. With a detailed but always keeping it simple and informative review. So we can be useful for most of you guys!

Let´s start by clearing some common out of the way, and also going through some of the fundamentals here:

 

What is synthesis?

Sound synthesis is the process of using electronics to create an electrical pressure soundwave from scratch and then controlling and modifying it.

 

What is an Oscillator?

An Oscillator is an electronic sound source. It is the device which creates the electrical pressure soundwave in a synthesizer. Oscillators can be analog or digital.

 

CV, gates & MIDI

Before digital control, analog synthesizers used an interconnecting arrangement of controlled voltage/gate signals to trigger their various components.

For example, a key/note played on a keyboard would send a control voltage to an oscillator to tell it what pitch to produce, and another control voltage to an envelope which in turn would "instruct" an amplifier "shape" the volume envelope of the sound as it emerged from the oscillator.

Since the early 1980s, MIDI has been the primary way to control and play a synthesizer from an external controller, and internal digital interconnection has replaced the internal CV/gate control signals.

 

Patches

In the early days of synthesis when only modular systems were available, sounds were created by connecting modules with patch cords and adjusting settings on each module. The settings and patch cord connections for a sound came to be referred to as patches. Recalling a patch was a laborious process until performance synthesizers began to integrate microprocessor control and ROM memory was developed to store a patch configuration digitally.

There is still no way to store a patch created with a modular analog system.

 

Types/methods of synthesis

The basic concept behind any synthesis is that you are working primarily with 4 basic waveforms:

 

 

Layering and modulating them with each other in certain frequencies. Then you shape the sound with amplifiers and filter envelopes to achieve desired longevity.

You are used to identifying musical intervals by their specific ever-present sound quality. You can do the same with waveforms. Virtually any synthesizer on the market uses the four basic shapes.

 

We recommend you to spend some time playing those back and their sound will become apparent to you!

 

Here are the four waveforms played in different octaves so you can hear the difference between them:

 

Sine

 

 

Square

 

 Triangle

 

 

 Sawtooth

 

   

Many different types of synthesis have been invented since the first successful (and affordable) commercial analog synthesizers in the late 1960"s.

Each of these has found an army of dedicated fans and provide a wide range of sonic possibilities. These synthesis types are responsible for the sound of today’s music, and if you want to keep up, you need to have at least a basic understanding of what they sound like.

Then you’ll be able to create your own musical timbres and unique sound!

 

The following are perhaps the best known ...

 

Wavetable

 

A wavetable is a collection of single-cycle waveforms, or essentially samples of audio, that get played back on a loop to produce a periodic waveform or a continuous sound or tone. The speed of which those waveforms are played back, or the speed between each loop cycle, determines what you and I would call pitch or frequency. and in the digitally audio world, a MIDI note is essentially what determines this speed. In a sense, wavetable synthesis can be thought of as a highly specific form of sampling. But with the intentions of quickly morphing and animating between the different single-cycle waveforms, within those samples over time.

Wavetable Synthesis employs the use of a table with various switchable frequencies played in certain orders (wavetables). As a key is pressed, the sound moves in order through the wavetable, not spontaneously changing the waveform, but smoothly changing its shape into the various waves in the table.

This method produces sounds that can evolve really quickly and smoothly. The method was intended to create digital sounding noises, so it is not used for instrument replication very often but is an effective way to create pads or harsh-sounding tones like bells or digital sounds.

 In fact, it takes all the waves you are likely to ever want to produce (at least that a particular synth is capable of) and stores them in different tables.  Then when you want to reproduce a certain sound, the synth loads the wave for that sound and plays it over and over again.

Why would you want to generate sounds this way?

Less memory:  Especially when digital synthesizers first came out, memory was small and expensive.  You can store many waves at full resolution without taking up too much precious memory because you only need to store one period of the wave.

Less processor power:  Fast computers were big and expensive, and calculating what two waves would do when added together or how a filter would affect a wave is computationally intensive.  With wavetable synthesis, all the different waves are pre-calculated and stored in the tables.

 

Visual representation of a wavetable with several different waves stored in it. The "table" is from the Circle soft synth by Future Audio Workshop.

 

Wavetable is one of the latest developments in sound design and modern synthesizers utilizing this synth type often pair it with other synthesis types like Granular, FM, Subtractive, Additive, etc. To make more complex waveforms in real time.

This type of synthesis offers the widest range of sounds that can be created comparing to any other technique.

With the release of Native Instrument’s Massive and also Xfer’s Serum, wavetable synthesis became one of the most flexible and popular methods of achieving a diverse palette of sounds fast. Although, they are both wavetable and subtractive.

 

 

 

If you want to discover how much synthesizers can offer, both of them will satisfy pretty much any sound design need as it combines the most popular features in one.

And now also you can consider the new Wavetable device on Ableton live 10!

 

 

 

Subtractive Synthesis

 

Subtractive is the most common method that gave birth to the concept of sound synthesis. And is also one of the most popular synthesis types of all, perhaps due to its inherent simplicity and application.

This type of synthesis is a very simple signal chain of an oscillator (or the combination of multiple oscillators) running through a filter (EQ curve) which is then sent to an amplifier for gain staging and ADSR (attack, decay, sustain and release) for controlling the envelope response. The harmonics present within the oscillators tones can be whittled into harmonic structures that mirror those of actual instruments.
This method is very easy to achieve in both analog and digital realms and can be used to create numerous (possibly infinite) instruments, effects, and sounds.

The analog subtractive synthesizer was initially designed for this purpose–as an alternative to hiring musicians to play on recordings, however, it quickly morphed into its own instrument, creating various sounds never before made by any acoustic instrument.

Subtractive synthesis is the most closely associated with the analog synthesizers of the ‘60s and ‘70s.  In which the harmonics of simple waveforms, such as the ones previously mentioned, are attenuated with a voltage-controlled resonant low-pass filter.

Some of the Vintage synths most known in this type are the Minimoog, and the Korg Ms-20, maybe you recognize them!

 

 

 

 

In many ways, it’s a similar process to the way the voice works. The vocal notes are the ‘oscillator’, and the mouth acts as a filter, reducing the harmonics heard according to how widely it is opened.

This type of synthesis sounds very vintage, and very obviously synthetic, which is a big part of its appeal (think Kraftwerk, the BBC Radiophonic Workshop, and just about every dance music track ever for an idea about its sound).

Subtractive synthesis is a great way to learn about how synthesis works.

Roland’s GAIA synth and Reason’s Subtractor are great subtractive synths to learn on.

 

 

 

Basic subtractive synthesis utilizes waveform changes, filtering, and envelope adjustments.

One of the main controls on a filter is “cutoff frequency”, which sets the point where the filter starts blocking frequencies.  There are several different types of filters which may block frequencies lower, higher, or right at the cutoff frequency:

• Low-Pass: Removes frequencies above the cutoff frequency.  Makes waves sound darker or muddier.
  
  
• High-Pass: Removes frequencies below the cutoff frequency.  Makes waves sound brighter.
  
  
• Band-Pass: Lets a narrow band of frequencies centered around the cutoff frequency through.
  
  
• Notch / Band-Reject: Removes a narrow band of frequencies centered around the cutoff frequency.

 

 

Additive

 

Additive synthesis is a sound synthesis technique that creates timbre by adding sine waves together. What this type of synthesis does, is trying to achieve the same result as Subtractive Synthesis, but approaching the method from a “constructive philosophy”, rather than just carving harmonics out.

The sounds that are heard in everyday life are not characterized by a single frequency. Instead, they consist of a sum of pure sine frequencies, each one at a different amplitude. When humans hear these frequencies simultaneously, we can recognize the sound.

This is true for both "non-musical" sounds (for example, water splashing, leaves rustling, etc.) and for "musical sounds" (e.g. a piano note, a bird's tweet, etc.). This set of parameters (frequencies, their relative amplitudes, and how the relative amplitudes change over time) are encapsulated by the Timbre of the sound.

Rather than presenting a wall of harmonics and carving out the harmonic structure desired (Subtractive), in additive synthesis multiple sine waves of varying levels and frequencies are combined together to build the harmonic structure desired. Simply put, instead of starting with everything you need and throwing away what you don’t need, you start with nothing and build harmonic structures from scratch.

The process of Resynthesis is highly connected to Additive Synthesis. In essence, Resynthesis involves analyzing the harmonic structure of a sampled sound and trying to recreate that structure. Additive Synthesis is essentially Resynthesis, excluding the fact that Resynthesis is the recreation of a specific existing sound, not a general instrument tone. Given this connection, additive synthesis is quite often used in Resynthesis processes.

The vintage version of a hardware additive synth would be the Fairlight CMI. Released in the 80´s.

Which is well simulated by Arturia in their latest version vst, or the Analog lab 3.

And then there is the Kawai K5000.

One curious thing to have in mind is that the additive synthesis uses the same principle that Hammond Organs use!

While its true Organs synthesis sounds similar to K5000, it's true to say that a K5000 can produce a more varied palette. Although the synthesis approach on both is similar, Organs usually only employ a small number of sine generators (they were created before). The K5000 has 64 per voice and a Formant Filter. 

But you have more complexity achievable sounds in a synth like this one for sure!

 

 

FM

 

FM (Frequency Modulation) synthesis was one of the first digital synthesis methods. It first appeared in the legendary Yamaha DX7.

The way that FM synthesis works is that a simple waveform called a carrier (sine, saw, square, triangle) is modulated by another wave, called a modulator. The result is a far more complex waveform. This type was the first commercially successful, and affordable, digital synthesis type. Just like Subtractive Synthesis FM also relies on using basic 4 waveforms (Sine, Square, Triangle or Sawtooth) plus their variations to achieve the desired result.

These waves are known collectively as operators, and an FM synth can have many operators to shape its sound to increasingly complex waves.

The main advantages of FM were that waves of unprecedented complexity could be produced. In particular, sounds with bell-like qualities could be produced with a level of authenticity never heard before.

Today, the most popular of all FM synths is Native’s FM8, available in the Komplete packages (which will also provide great examples of all the types of other types of synthesis also mentioned here). If you want to add a bit of an ‘80s vibe to track, this is a really authentic and easy way to do it.

 

The guys from Arturia also made a good vst recreation of the Yamaha DX7 sounds called DX7 V. You can purchase it completely separate, or in a bundle version among other types of synths in the Analog lab 3 plugin.

It is similar to Additive synthesis in that it uses 6 sine wave creating oscillators, each of which can have their frequency, amplitude, and envelope (volume over time) set by the user. In FM, oscillators are called Operators. It differs from additive synthesis in the fact that rather than combining the waves together, the output of one operator is sent to modulate, or "wobble", the next. The second then modulates a third and so on until a complex waveform is produced by the final oscillator in the chain, the so-called Output Operator.

 

 

Find your own Sound

 

With these four synthesis types, you can create almost any sound you want. In the modern computer-era, the availability of VSTs in the market offers plenty of choices to pick from on our constant search to discover new sounds we´re all in. Contemporary music is always hungry for new timbres.

Synth plugins are going to be your best friends here.

With such a vast abundance of delicious possibilities, how do you choose? Numerous artists have chosen to start with a more limited palette and slowly build into a unique sound. Once you have trained your ears to recognize the different types of synthesis and how they are produced, you too can grow your own mind-blowing sound!

Many of these synthesis methods are combined or layered within single programs to accommodate the creation of unique synthesizers. In understanding these methods, experimenting, and combining them, you´ll end up becoming the creative force behind sound-synthesis.

 

We will be talking more about this subject in our next articles, there is a world of data around the whole synths world, and it can get very confusing sometimes.

So, you can let us know which is your favorite here in the comments if you need a hand or have any doubt. We´re glad to be helpful!

 

 

 

Here is some knowledge to have in mind when you are starting your production process, and you can´t choose between this types:

 

All different types have their strengths and weaknesses, so we recommend you all to just familiarize yourself with each type of synthesis and you'll get a feel of what results you´ll get!