ï~~Stochastic Music Xenakis
Marie Helene Serra
CEMAMu
fax 1-45-29-65-31
ABSTRACT
The purpose of the paper is to give more details about the recent computer research of
Mr.Iannis Xenakis in stochastic research last year in Montreal (see the paper written by Mr.
Xenakis in the ICMC 91 proceedings).
My contribution will emphasize the use of the probability theory in the musical
composition. I will focus on the computer program that Iannis Xenakis has written in 1990
(the program is still in progress). This program has been used for the composition of two
pieces (GENDY301 premiered in Montreal, October 1991, and GENDY3 premiered in
Metz, November 1991). The program is applying stochastic laws at two levels of the
composition: the sound synthesis algorithm is called dynamic stochastic synthesis; this
algorithm computes directly the numerical samples of the sound (with no reference to the
Fourier theory) by distorting an initial waveform with stochastic variations. The
macroscopic organization of the musical piece is also depending on stochastic laws: for
instance the time distribution of the different voices are computed with the exponential law.
The probability theory is used in computer music for different reasons and for different
musical goals. I will present other examples of the use of aleatory calculus in
contemporary computer music.
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