Music Generation through Cellular Automata: How to Give Life to Strange Creatures

Cellular Automata (CA), like every other dynamical system, can be used to generate music. Starting from any initial state and applying to CA simple transition rules, such models are able to produce numerical sequences that can be successively associated to physical parameters. This approach is interesting because, maintaining fixed the set of rules and varying the initial data, many different, though correlated, numerical sequences can be originated, which in turn can be translated into music. In fact, a rendering process can tie one or more physical parameters to these numerical sequences, creating musical compositions. Furthermore, a genetic algorithm (GA) can be utilized to promote their evolution, giving birth to a process of progressive refinement of the musical compositions. The aim of this paper is to present a series of musical pieces generated by CA. The first section of the paper has been devoted to the effects coming from the application of various rendering processes to one dimensional binary state CA. Typical behaviours of automata, belonging to each of the four classes discovered by Wolfram, have been studied: CA evolving to uniform state, CA evolving to a steady cycle, chaotic and complex CA. Musical Dreams, the system for the simulation and musical rendering of one dimensional CA, has been used in analyzing the resulting patterns and in discovering strange creatures in the artificial worlds. In the second section of the study, various CA, obtained both by random generation and by the preceding analysis, have been organised into families and, successively, evolved through a genetic algorithm. Harmony Seeker, a system for the generation of evolutionary music, based on GA, let us improve our musical compositions. The obtained results vary depending on the rendering system used. In general, automata belonging to the first of the Wolfram’s classes, seem well fit for the production of rhythmical patterns, while elements belonging to the second and the fourth class seem to produce better harmonic patterns. Chaotic systems have produced good results only starting with simple initial conditions (IC). Experiments made in the second section of the study have produced acceptable harmonic results with CA belonging to the second Wolfram’s class.