A cellular automaton (CA) is an array of identically programmed automata, or "cells", which interact with one another. Its state is a variable that takes a different separate for each cell. The state can be either a number or a property. For instance if each cell represents part of a landscape, then the state might represent (say) the number of animals at each location or the type of forest cover growing there. Its neighbourhood is the set of cells that it interacts with. In a grid these are normally the cells physically closest to the cell in question. Musicians have used CA to aid in the control of structures at macro- and micro-levels.
(Source - http://life.csu.edu.au/complex/tuto... - Note: this source has been discontinued.)
UNESCO DigiArts- Digital Music online course: Introduction to Cellular Automata Music Research ( English )