The Evolution of Granular Analysis and Synthesis

Curtis Roads (University of California, Santa Barbara, USA)

It could be instructive to demonstrate a range of research and artistic creation emerging from our laboratories in Santa Barbara over the past five years. All of this research is ultimately based on a scientific model of sound initially proposed by Dennis Gabor, and soon afterward applied to music by Iannis Xenakis.

Granular analysis (also called atomic decomposition) and granular synthesis has evolved over more than five decades from theories and primitive experiments into a broad range of applied techniques. Specific to the granular model is its focus on the micro time scale (typically 1 to 100 ms). Granular techniques treat sound as a stream of acoustic particles in both the time domain and the time-frequency domain.

In this lecture, I will first very briefly trace the history of the idea of sound particles. Next I will demonstrate PulsarGenerator, an application developed by Alberto de Campo and me in 2001 for a specific type of particle synthesis with links to past analog techniques. I will also demonstrate the SweepingQGranulator, a tool that I wrote in the SuperCollider language for the microfiltration of granulated sound.

The latest threads in this line of research go in two directions. The first is a time-frequency analysis method known as matching pursuit decomposition. The second is a new prototype for generalized synthesis and control of particle synthesis called EmissionControl.
 
Finally, I would like to demonstrate some of the visualizations that we have been developing in conjunction with this research, some of which are motivated by scientific aims, others of which are artistically motivated, and some that attempt to satisfy both aims.

The idea that a continuous tone could be decomposed into smaller quantities of time emerged from ancient atomistic philosophies. In the latter part of the fifth century BC, the Greek philosophers Leucippus and Democritus taught that all matter consists of atoms separated by empty space. They speculated that any substance or energy could be divided into smaller and smaller pieces and would eventually reach a point where it could no longer be divided: the atom. Another atomist, Epicurus, founded a philosophical school in Athens and taught his doctrines to a devoted body of followers. Later the Roman Lucretius wrote a poem De Rerum Natura that delineated the Epicurean philosophy.

In the seventeenth century, at the dawn of early modern science, the French thinkers Pierre Gassendi and René Descartes revived atomism. A confluence of intellectual energy, emanating from Descartes, Galileo, Beekman, Mersenne, Gassendi, Boyle, and others, gradually forced a paradigm shift away from the Aristotelian philosophical point of view toward a more experimental perspective. Issues in acoustics were central to the growth of science in western Europe.

The modern concept of sound particles can be traced to Einstein's phonons, which he predicted in 1907. But the phonons consist of inaudible packets of ultrasonic energy at feeble amplitudes. It was Einstein's pupil, Dennis Gabor, who in the 1940s had the fundamental insight that brought the particle model into the domain of perceived sound. The composer Iannis Xenakis learned of Gabor's experiments, and in 1959 he made an experiment in which he approximated granular synthesis by means of tape splicing. He did not, however, continue research in this direction. His book Formalized Music described a theory of granular synthesis, and it was this description that led to me realize granular synthesis on a computer in 1974.

Today granular synthesis is a staple of electronic and computer music technique.