Studio Slave Explain The Different Types Of Synthesis Used In Many Popular Synthesisers
As technology has evolved, plenty of new techniques have been discovered for sculpting and synthesising sounds. Many of these sound design practices and techniques lend themselves to certain sounds.
We understand that this can all be a bit confusing for the new music producer, so in this article we aim to uncover the different types of synthesis as well as some pointers on which synths to use when trying to create or emulate certain sounds.
Before we delve into the different types of synthesis we will briefly cover some basics to all types of synthesis.
Nearly all synthesis types have the same basic flow. We have the sound source, this can be a sample, a sound generating oscillator or an operator. This is what is going to generate our initial tones. These tones can be mixed with other sound sources, in the case of fm synthesis the sound sources are modulating one another.
From the oscillators the signal will usually go to a filter or set of filters where you can sculpt the sound in various ways. Many of these filters will have a filter ADSR envelope which can be assigned to further sculpt the signal over time. The signal is then passed onto the amp section. From here the signal can be amplified and an amp ADSR envelope can be applied to give the signal its final shape.
The signal is then passed onto the output. This covers most synthesisers in their most basic form, there are plenty of extras that comes with synthesisers though such as modulating capabilities, LFOs, pitch envelopes and FX. As you learn your synthesisers and plugins you will begin to understand how you can incorporate these tools into your sound creating Arsenal.
A basic subtractive synthesiser flow diagram
Additive synthesis is the type of synthesis which most closely emulates how sounds are produced in nature. Lots of sine waves at different frequencies are summed together to make complex waveforms. The problem with these synthesisers is that natural sounds are very complicated in their harmonic structure over time, so to accurately recreate a natural sound hundreds of individual sine-waves would need to be used which is why it was not used very often before the digital age but now was computer CPU becomes more powerful we are seeing a re-emergence of additive synthesis in software VST and AU form. Many new VSTs are boasting the power of a combination of different synthesis including the ability to load your own sounds into the synthesiser which then re-synthesises the sound using additive synthesis, allowing you the flexibility to edit the sound on an individual sine wave basis.
Logics Native alchemy plugin, which is capable of complex additive synthesis.
Serum. another soft synth which is capable of additive synthesis however it is predominantly a wavetable synthesiser.
Subtractive synthesis generally uses analog circuitry, so is often referred to as analog synthesis. This is the easiest type of synthesis to learn for a beginner. Subtractive synthesis works by starting with a complex waveform and subtracting sound away from it to give you the sound you want. Usually the sounds are made with between 1 and 3 oscillators and these will then be passed through filters where the sound can be filtered and sculpted into the final sound. As you can imagine the types of filters used are crucial to the end result as well as the envelopes used.
Subtractive synthesis generally creates very rich warm sounds (think anything Moog) however due to the analog circuitry there was often imperfections in drift and tuning.
A subtractive synthesiser from Korg
The Moog Little Phatty
Fm synthesis was the first affordable method of digital synthesis. It is renowned for making very realistic and harmonically rich sounds, in particular it is very good at emulating bell, glass and metal instruments. In FM the oscillators are called operators and rather than adding them together they can be set to modulate each other. The routing in which they are set to modulate is known as an algorithm and this makes a large impact on the final sound. One of the operators will be the carrier which is the main operator getting modulated.
Typically FM synthesis comprises of between 4 & 6 operators. These will then feed into the filter and amplitude envelopes to be shaped much like subtractive synthesis would. The more you feed the volume of a modulator into a carrier, the brighter and richer in harmonics the resulting sound will become.
FM synthesis can be tricky to get your head around at first but it is well worth spending the time to do so. The fundamentals are to keep your oscillator ratios as whole numbers to keep your sounds harmonic. If you wish to make dissonant off key sounds then use ratios that aren’t whole numbers. This is how many drum samples are created such as kicks and snares.
The Yamaha DX7, an iconic FM synthesiser.
Wavetables synthesis is similar to subtractive synthesis, however instead of using oscillators the synthesiser will have a table of different waves built into its memory. You can use wavetable positioning knobs to blend between waves. you can then filter and subtract the waves down to the final sound as normal. Due to the ability to blend the wave over time, wavetable synthesis is perfect for creating lush evolving textures. A common wavetable synth plugin used today is native instruments massive.
Physical modelling uses fast processors commonly known as DSPs to quickly convert digital to analog signals in real time. It simulates the physical properties of natural instruments. The physically modelling data is programmed to be manipulated by the user either using a computer or by midi on a keyboard or synthesiser. More recently physical modelling synths have been completely in the box due to faster host processing capabilities of new computers.
Applied Acoustics Systems Chromaphone, A physical modelling software synthesiser.
Ableton’s Collision instrument also implements physical modelling technology to replicate a range of realistic timbres.
Granular synthesis is where a sample is cut up into tiny grains. These grains can then be manipulated either by duration, size, amount, pitch or amplitude. These can be used to create some completely crazy sounds. This type of synthesiser typically lends itself to long evolving textures and soundscapes due to its time stretching capabilities
PCM synthesis or pulse code modulation is where a part of a sound is stored within the sampler. This is usually the attack transient of a sound as an entire sound would take up too much space and this would also limit the amount of different sounds you could synthesise from the attack transient. This attack transient is then blended with a tone that forms the latter part of the sound. This sound can then be filtered down and processed. This type of synthesis was used very successfully be Roland and is a relatively cheap type of synthesis to manufacture. More recently this type of synthesis has been used in the Korg Volca series and is very good at effectively emulating percussive sounds.
PHASE DISTORTION SYNTHESISERS
Phase distortion synthesis was used extensively in the Casio CZ series which was a very prized synthesiser. The fundamentals is that a sinewave will be manipulated with an algorithm to alter its phase and distort it. As this signal is distorted extra harmonics are created which can then be filtered down.
In todays digital world many software companies are putting a lot of thought into the design of their new super synths. These have the ability to emulate any combination of types of synthesis as well as the ability to blend between them (a form of vector synthesis)
We can see this in action using Ableton’s new max for live instrument MULTI as well as in Logics brand new native plugin ‘alchemy’.
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