Synthesis
Put simply, synthesis is the process of creating musical sounds using different combinations of waveforms, filters and audio effects.
Specification 👇
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How Synthesis Is Used To Create Sounds
Synthesis is “electronically creating musical sounds using oscillators and filters.” It is the mixing of waves and combinations of filters and effects that make a sound unique.
Let's imagine that you are baking a cake; you start with some ingredients and, through a range of different processes, they are combined together and you end up with a cake.
In synthesis terms, you start with either a basic waveform or white noise. Then you need to decide what type of synthesis you’re going to use to make these non-musical noises into musical sounds. You can then fine tune this sound with LFOs, filters and envelopes.
Waveforms and White Noise
There are five waveforms that you need to be able to name and identify; sine waves, square waves, triangle waves, sawtooth waves and pulse waves. In a synthesiser, these waves are generated by an oscillator.
The sine wave is a smooth, curved wave. It’s known as a pure wave because it doesn’t have any harmonics.
Square waves are, unsurprisingly, square shaped waves. They sound pretty similar to sine waves, but the difference in sound lies in the addition of odd harmonics.
Triangle waves, much like square waves, are named as they are due to their shape. They also have harmonics (odd only, similar to square waves) but they roll-off or lose their amplitude far quicker.
Sawtooth waves are named due to their resemblance to the teeth on a saw. This wave has a harsh sound as, unlike square and triangle waves, it is constructed from not only odd harmonics but even harmonics as well.
Lastly, pulse waves. They are similar to square waves in shape, but the duty cycles are different. A square wave has a duty cycle of 50%, meaning that it’s ‘on’ 50% of the time and ‘off’ 50% of the time. A duty cycle of 70% would mean that the wave is ‘on’ 70% of the time and ‘off’ 30% of the time.
White noise is a noise that covers the whole frequency spectrum. Sounds like someone going “shhhh” really aggressively.
Types of Synthesis
Additive synthesis involves the combining of sounds, such as multiple waveforms.
Subtractive synthesis is the removing of frequencies via filters. This techniques lends itself well to white noise.
Frequency modulation (FM) involves using a wave or oscillator to change the frequency of another. This is quite a confusing concept but there is a very good article here from Music Production Nerds to help explain.
Granular synthesis is a bit like sampling. You take a little ‘grain’ of sound and duplicate it multiple times over.
Wavetable synthesis is when an isolated loop of a wave is stored in a table so that it can be recalled at anytime.
LFO’s, Filters and Envelopes
A low frequency oscillator, or an LFO, is “a signal that oscillates below audible frequencies and found on a synthesiser and modulation based effects. Commonly used to modulate other elements of a sound."
In other words, an LFO is produced by an oscillator that has a very low pitch (20Hz or below, so out of human hearing range). These oscillating waves are used to modulate a parameter in a synth or sampler or effects processor. For example, if the volume of a wave (produced by an oscillator) is modulated with an LFO, the result is tremolo.
There are two types of filter that you need to know about when it comes to synthesis; high pass filters and low pass filters.
A high pass filter is “a type of filter that removes only bass frequencies below a set point (cut-off frequency) and allows high frequencies through unaffected.”
A low pass filter is “a type of filter that removes only treble frequencies above a set point (cut-off frequency) and allows low frequencies through unaffected.”
Sound envelopes are used to affect how a parameter applied to a sound changes over time. For example, in your DAW you can, using an envelope, automate how the panning of a track changes. This type of envelope can apply to a whole series of notes.
Synthesisers on the other hand, only really use one type of envelope; ADSR. It is a volume, or amplitude, envelope and affects just one sound at a time. Keeping reading for more information.
How Timbre Can Be Manipulated by a Wider Range of Parameters
ADSR
ADSR, standing for attack, decay, sustain, release, is an amplitude envelope that changes the volume of a note at different points within its playing time.
Attack controls “the length of time it takes between a note being started and the point at which it reaches its peak."
The decay control determines “the amount of time that it takes for the peak to drop down to the ‘sustain’ level.“
Sustain refers to “the volume at which the note is held until the key is released."
Finally, release controls “the length of time that the note continues after it has stopped being played until it dies away to nothing."
Cut-off Frequency
Cut-off frequency is the point at which a filter is engaged, or rather when frequencies begin to be cut. The diagram shows the cut-off frequency of a low pass filter, but this can be applied to high pass filters too. The Q value affects the steepness of the curve of the filter.
Resonance
Resonance, or a resonant frequency, is a frequency that is louder than other frequencies. It often occurs near to the cut-off frequency.
Course and Fine Tuning
You can control the tuning of a note using the course and fine tuning controls. Course tuning allows you to change the pitch of the notes by any number of semitones. Fine tuning alters the pitch by any number of cents.
Pitch Bend Range
The definition of a pitch bend range is pretty self explanatory – it is the extent to which you can bend the pitch of a note.
Monophonic vs Polyphonic
On a synthesiser, you can switch between monophonic and polyphonic mode. Monophonic mode allows you to only play one note at a time, much like a flute operates for example. In polyphonic mode, you can play multiple notes simultaneously, like a piano can for instance.
Portamento
Portamento is the sliding between notes. This control makes it so that when you play one note after another, all the notes between these two notes are played quickly in ascending or descending order to create an interesting transition.
Arpeggiator
An arpeggiator treats the note you are playing as the root of a chord and automatically plays the individual notes of that chord as an arpeggio/broken chord.