Dissertation abstract:
Autonomous instruments are computer programmes that generate music algorithmically and without realtime interaction, from the waveform level up to the large scale form. This thesis addresses questions of aesthetics and the role of the composer in music made with more or less autonomous instruments. Furthermore, a particular form of autonomous instruments, called feature-feedback systems, are developed. These instruments use feature extractors in a feedback loop, where features of the audio output modulate the synthesis parameters.
Methods adopted mainly from chaos theory are used in experimental investigations of several feature-feedback systems. Design principles are also introduced for controlling limited aspects of these instruments. These experimental methods and design strategies are not widely used in current research on synthesis models, but may be useful to anyone who wishes to build similar instruments.
Whereas Varèse preferred to designate music as “organised sound”, autonomous instruments may be said to engender self-organised sound, in the sense that the result was not specified in detail by the composer—in fact, the result may not even have been expected. Thus, there is a trade-off between a deliberate sound-shaping by the composer on the one hand, and truly autonomous instruments on the other. The idiomatic way of operating an autonomous instrument is experimentation followed by serendipitous discovery.