  The Number Pieces are a corpus of works by composer John Cage, which rely on
a particular time-structure used for determining the temporal location of
sounds, named the "time-bracket". The time-bracket system is an inherently
stochastic process, which complicates the analysis of the Number Pieces as it
leads to a large number of possibilities in terms of sonic content instead of
one particular fixed performance. The purpose of this paper is to propose a
statistical approach of the Number Pieces by assimilating them to stochastic
processes. Two Number Pieces, "Four" and "Five", are studied here in terms of
pitch-class set content: the stochastic processes at hand lead to a collection
of random variables indexed over time giving the distribution of the possible
pitch-class sets. This approach allows for a static and dynamic analysis of the
score encompassing all the possible outcomes during the performance of these
works.
