Technologies dedicated to the dynamic processing of signals in the audio-frequency band have enabled the musician to handle accurately the individual parameters of sound. The composition and sophisticated control of sound, rendered intuitive by high-level software applications, have made possible an artistic and creative approach which has laid the basis for a rapid evolution of the language of music and of its associated applications.
Among the lines of scientific research stimulating the imagination of contemporary musicians, those which study the propagation and perception of sound have acquired a particular importance. Control of sound diffusion sources in relation to the physical space within which the sources radiate and knowledge of how the human perceptive system reacts to the stimuli of musical phenomena; these represent today the targets for cognizance and artistic expression. In the field of music, the acoustic instruments generating sound have always been correlated to the space for which they are destined and to the conditions of listening; music has used variables of the highest intelligibility (pitch, duration, intensity) for structuring the grammar and syntax of the language, tempered on the basis of perception. Only today, however, can the musician have at his disposal effective analysis tools for investigating the complex interaction of these variables and for consciously directing their effects towards expressive aspects that involve, on the one hand, the timbre and, on the other, the physical space occupied by the sound phenomenon.
This last-named aspect is presented and discussed in the paper, concentrating on the physical and perceptive characteristics which define the domain of the space and of its musical utilization. Some technological solutions will be examined (Planephones, Holophones, Waveguides) as well as more typically perceptive aspects (inter-aural variations, directive bands, distance, movement) so as to analyse recent applications of sound spatialization (wave front sculpture) and the expressive significance assumed by composition of the listening space in the musical language (Art sound and functional installations).
The paper is also accompanied by examples of performance in order to illustrate the musical approach to the nature of the problem: from the way in which the musician foresees the spatial result of a sound event to the simulation models, to the specifications included in the score for diffusion of the sound.
A series of musical extracts (in audio digital 2-channel format, CD) is presented with the paper in order to give an example of the types of sound signals composed specifically for spatial treatment and for evidencing and describing the parametric control applied to them.