The perceived amplitude of a sound is used as a compositional tool in different situations. It can be used to establish the role of a sound in context, to exaggerate or diminish its importance in order to focus the listener's attention. It can be also employed to push a sound forward to give it presence, or in the background in order to blend it with other sounds and create texture, or match the level with the level of other sounds to create a wall of sound.
In Musique Concrete composers make use of dynamic contrast in order to change the size of sound objects over time and move them in the three dimensional audible space determined by the listening environment.
Bernard Parmegiani uses this technique extensively in 'Dynamique de la Resonance' and 'Ondes Croisees' (Parmegiani, 1975). Sounds from different sources appear in succession at different levels, which separates them in space. Most often the attack of a sound is loud, and while it decays to the background level, another sound suddenly appears. New elements appear at different intensity levels, much louder than the background. The listening volume of the composition is suggested from the start, determined by the high intensity of the first sounds. The listener is prepared to hear more sounds at that intensity and the silence between the sounds creates tension.
From a perceptual point of view this technique is used to alter the emotional state of the listener. This phenomenon has its origin in the early evolution of man, when very acute senses were a necessity to spot danger and react as fast as possible. When the perceived volume increases suddenly, the sounds come unexpectedly, the composition creates expectation, plays with tension and release.
The compositions 'Half life' by Curtis Roads and 'Agon' by Horacio Vaggione are made from sound collages (rapid successions of sounds) that morph into unique acousmatic sound objects with strong individual characteristics which resemble living organism of unknown origin or of bio-mechanic nature.
The technique used to create these sounds is described as 'micromontage' by Curtis Roads (Roads: 2001, 181:187).
The term '"montage" derives from cinema, where it refers to a sequence of rapid images connected through cutting, splicing, dissolving, and other editing operations. (Roads: 2001, 183)
For the acoustic approach the composer extracts short segments of sounds with different characteristics from a range of acoustic instrument recordings. These sounds are edited (duration, amplitude, harmonic content, spatial information) and restructured to create new sounds. Manually arranging the particles gives the composer greater control over the quality and evolution of the sounds than running an algorithm, however this is tedious work.
The automatised version of micromontage is granular synthesis, where short segments of sounds, called grains, are grouped based on their descriptors, and used as building blocks for creating individual sounds or texture.
The textures created with micromontage sound different to both stereo and mono because individual segments are arranged asynchronously in the stereo field. The same portion of a sound played in the left channel overlaps an identical copy played in the right channel with a slight delay. This is in theory a difference in phase, and because it is changing over time in a non-linear way it creates the psychoacoustic effect of immersion.
In Autechre's track “IV VV IV VV VIII” (Autechre, 2003) the rhythmic elements are constantly playing with the listener's anticipation and expectation.
Both at micro and macro (whole composition time) level changes occur when the rhythm starts to become familiar or at least less coded. Thus it can: morph into a different pattern; change suddenly; stop completely; slow down while presenting only some of the previously used elements.
There are several areas in the composition which contain blocks with a perceivable rhythmic pattern. At block level, the beats are anchored with melodic parts and sound very organic. These appear to be interrupted and to not adhere much to a musical time as to follows an inner cycle. The composition at times seems to have different time levels superimposed, but these are not obvious. Each rhythmic block seems to go towards an ending, but the closure never comes. The start and end points appear to overlap. As the rhythm vaguely reveals itself, becomes more familiar forming a recognisable pattern, it mutates, transforms into a new chaotic pattern.
Perceptually this continuously opens an expectation, demands for an interpretation. The balance between randomness, repetition and misplacement is calculated so that it's always on the point of disintegrating. Before that happens, stability comes for a short while, followed again by another undecipherable sequence.
Parmegiani, B. 1975. De natura sonorum (1975) (version integrale): suite in twelve movements: 'Dynamique de la Resonance' and 'Ondes Croisees' INA GRM, 2001: CD
Autechre. 2003. Draft 7.30: IV VV IV VV VIII. London, Warp: CD
Roads, C. 2001. Microsound. Cambridge, Mass. ; London: MIT, 2004 Accompanying CD-ROM track 7 and 11
Roads, C. 2001. Microsound. Cambridge, Mass. ; London: MIT, 2004