With historical roots in the work of composer Iannis Xenakis, this term is currently strongly associated with the work of Curtis Roads. Broadly, the term refers to conceiving of and representing sound in terms of particles. These sounds fall within the domain that Roads calls the "micro time scale". He defines this scale as one that embraces transient audio phenomena, a broad class of sounds that extends from the threshold of timbre perception (several hundred microseconds) up to the duration of short sound objects (ca. 100 milliseconds). Roads has recently published a book entitled Microsound (Cambridge, MA: MIT Press, 2001).
Tiny particles of sound, small chunks that fall between the gaps, but which can join together to create large sounding objects.
Micro- to Macro- sounds
When we bring micro-sounds together we create macro-sounds, larger structures of sound. These macro-sounds can themselves be built into larger structures.
Building macro sounds in this way, from individual grains upwards, gives the composer great control over the final outcome. And the process is greatly helped by computer and electronic technology.
The most important processes for this music are:
Additive and Subtractive Synthesis,
and Granular Synthesis
Grains of Sound
Imagine the grains of sand on a beach. Each of them is very small, but together they can form sand castles and even mighty sand dunes.
Grains of sound are exactly the same. They are tiny particles of sound that, when combined together, can create fantastic new shapes and structures.
It’s often difficult for us to hear individual grains on their own because they are so small.
Masses of Sound
There are two main types of sound masses:
Fused blocks of frequencies – created by very closely packed pitches of sound.
Cloud textures – made from a mass of individual grains which swarm and flow together.
In both cases, the composer creates subtle transformations by altering the balance within the sounds over time.
Blocks of Sound
Within blocks of sound, the composer will subtly add or subtract pitches from within the sound mass.
Examples of such works include: Györgi Ligeti’s Atmosphères or his piece Volumina.
Clouds of sound are structured differently. These take the form of more fluid masses of sound, in which the individual grains of sounds flock and swarm, each flowing freely but within a certain trajectory.
Examples of such works include Xenakis’ piece Concrete PH or Bernard Parmégiani’s De Natura Sonorum
In these works there may be many individual sound clouds which merge together or divide from one another.
The properties of swarming clouds of sound allow them to merge seamlessly together with a simple cross fade.
Beyond the Limits of our Hearing
When sounds are shorter than 1/10th of a second (10ms) we can no longer hear them as individual sounds.
These tiny chunks of sound are beyond the limits of our hearing. So we don’t hear them begin or end.
Threshold is a term used to describe the limits of our hearing. If a group of sounds are shorter than our time threshold for hearing we will not hear them individually.
The same is true for sounds that are very close together in pitch. Beyond the pitch threshold we are unable to hear individual pitches.
This property allows us to merge sounds together in the construction of seamless masses of sound.
Roads, C (2004) Microsound. MIT Press
术语顾问/Consultant to terminology