Event and process in the fabric and perception of electroacoustic music : a comparative study of Xenakis's Bohor and Metastaseis

In previous work we have shown that acoustic intensity profiles can be strong predictors of continuous-response patterns of perceptions of change and affect expressed by classical and electroacoustic music. We studied a section of Trevor Wishart's Red Bird in depth, and began a study of Xenakis's Bohor. Bohor shares generic patterns of intensity change across the piece with many other electroacoustic (ea) pieces we have studied: crescendi are short, with a high rate of change of intensity, while decrescendi are longer and with slower rates of change. Here we used statistical techniques of time series analysis seeking to relate listener perceptions and acoustic properties of part of Bohor, and part of Xenakis's orchestral piece Metastaseis. Time series analysis models the ongoing process of the perceptual responses. We found that surface timbral features of the latter, such as tremelandi, brass entries, glissandi and silence, though related to acoustic intensity patterns, were separable influences on perception; they constitute perceptually important events. The basic acoustic features of the section of Bohor we studied are more homogeneous, and at least for listeners unfamiliar with the piece, perceptual responses correspondingly are slighter. Possible future developments in the study of perception of Xenakis's electroacoustic music, and ea music in general, are discussed.