GranulationofSampledSound.doc

Granulation of Sampled Sound The technique I have found the most striking in the way it facilitates moving inside a sound is real-time granulation of sampled sound (Truax, 1990a, 1994b). Briefly, the technique divides the sound into short enveloped grains of 50 ms duration or less, and reproduces them in high densities ranging from several hundred to several thousand grains per second. A dramatic alteration of the sound called time stretching is made possible with this technique in that it allows a sound to be prolonged by any factor with no resultant change in pitch. The principle of the technique is that the samples within the grain are identical in order to those found in the original (hence the absence of pitch change), but the rate at which the grains move through the original material may be arbitrarily controlled. The fact that the grains are enveloped prevents audible transients and allows arbitrary sections of the original material to be juxtaposed and combined freely. The effect may be called slow motion sound, as it was envisioned by filmmaker Jean Epstein in the 1940s, about the same time that physicist Dennis Gabor (1947) provided the theory about the grain as a quantum of sound appropriate to perceptual processing. However, granulation and its twin, granular synthesis, did not become a viable compositional tool until I was able to develop a real-time implementation in 1986 with a programmable digital signal processor (Truax, 1988) as part of the PODX system. Since 1987 I have used this technique extensively to process sampled sound as compositional material (Truax, 1990b, 1992b, 1994b, 1996a, 1996b, 1999, 2000), at first being limited only to short phonemic fragments, as in The Wings of Nike (1987) and Tongues of Angels (1988).However, since 1990, longer sequences of environmental sound have been used in pieces such as Pacific (1990), Dominion (1991), Basilica (1992), Song of Songs (1992), Sequence of Later Heaven (1993), Sequence of Earlier Heaven