Perturbations
for chamber orchestra
Needham Series
1979; 12:42 min.
The title of the composition derives from the idea of balance alternately perturbed and restored. Meant is the balance between the different syntactic and sonic parameters the music's score is based on. In this work, there is an overall tendency toward lesser overall diversity as the end of the composition approaches.
Perturbations is through-composed. It is based on a computer-generated score whose parameters (entry point, pitch, tone-height, loudness, density/chord size) follow seven degrees of order/disorder ("change" over time). <1> represents utmost discontinuity, while <7> represents maximal continuity.
The performance heard here is that conducted by Thomas Clark during a concert at the 1981 International Computer Music Conference, Denton, Texas, USA .