Granular Synthesis
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Granular Synthesis draws on the principle of amplitude synthesis (since a sound demands the addition of perhaps thousands of grains) and also offers possibilities for sound transformation. In addition to the direct synthesis of grains, acoustic sounds can be 'granulated', and the parameters of pitch and time then separated as in phase vocoding. One of the first composers to use the technique was the American Curtis Roads, who in the course of a series of experiments starting in 1975 composed several pieces using the technique either in part or, in the case of 'Prototype' (1975), throughout. More recent research by Barry Truax has concentrated on methods of controlling granular synthesis in real time. (Source - Richard Dobson (1992). A Dictionary of Electronic and Computer Music Technology. Oxford University Press.)
EARS 2:
Creating Grains
Grains can be made by cutting sounds into very small pieces.
These small pieces can then be reassembled in a randomised order to create a granular cloud.
Grains can also be made from very short bursts of noise or from electronic tones.
Properties of Grains
The main properties of a Grain can be described in terms of:
Duration – how long is the grain.
Envelope – what is the shape of the grain over time.
Timbre – sometimes called “Grain Shape”, this is inherited from the properties of the source sound.
Each of these characteristics will affect the quality of the granular cloud.
Duration
The length of the grain may vary from ten-milliseconds (10ms) up to a few seconds.
Long grains will retain a lot of the character of the original sound while shorter grains will begin to loose this character.
{IMAGE – Sound cards cut into very thin slices at one end, slowly extending to larger chunks}
The longer the duration of each grain the more recognisable individual grains become.
[SOUND EXAMPLE - Vary Grain Length]
Envelope
The shape of the grain over time will affect they way in which individual grains combine and merge themselves together.
[IMAGE - ENVELOPE]
Envelopes allow grains to merge together. The type of envelope chosen will affect the way in which the grains combine and will affect how much of the original timbre of the sound source we hear.
[SOUND EXAMPLE - Vary Grain Envelope]
Timbre
The timbre of the grain (which some people call the grain shape) is affected by the original source material from which the grain was cut.
Different source materials will create different grain textures.
[IMAGE - Different source materials (Sound Cards) being fed into a granulator to create ??? Granular texture]
BUT, the duration and envelope of the grains will also affect the final resulting timbre of the grain.
[SOUND EXAMPLE - vary grain source material]
Combining Grains
When we begin to combine grains into “clouds” the way in which the grains relate to one another greatly affects the quality of the granular cloud that is made.
We need to be able to describe the relationship between the grains.
We can talk of the:
Spacing – how big is the gap between grains.
Density – how many grains are there in one place (Density is discussed in more detail here).
{IMAGE – DENSE GRANULAR CLOUD} + {Sound Example}
{IMAGE – SPARSE GRANULAR CLOUD} + {Sound EXAMPLE}
From Grains to Sound Masses
Grains can be brought together in two different ways in order to create “sound masses”.
Blocks of Sound
They can merge to form larger sounding objects, surrendering their individual character into the new object.
There is little or no space between the grains and their envelopes overlap to create a seamless sound.
Properties:
Low Spacing
High Density
Clouds of Sound
They can be grouped together, still retaining their individual grain characteristic, in a granular cloud.
The grains form a cloud of sound, in which individual grains flock together but are still heard as distinct from one another.
Properties:
Higher levels of spacing
Lower levels of density
The types of grains used and they way in which they are combined, will affect the characteristics of the final sound.
Try using blocks and clouds of sounds within your composition. Can you imagine how they might be combined?
Perhaps a block of sound might shatter into a granular cloud.
OR a granular cloud might merge to form a block of sound?
Be creative!
Fact
The granulation process is also used within time-stretching algorithms. It allows us to time-stretch a sound without changing the pitch.
It works by granulating the original sound and then looping the grains. This extends the sounds without changing the pitch.
Encyclopedia:
A method by which sounds are broken into tiny Grains and then reassembled and reorganised to form other sounds.
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