Program Notes

This piece is one of a family of compositions all bearing the “ST” title, an early project for Xenakis. “ST” stands for “STochastic,” a mathematical term meaning that something is randomly determined. In this family of compositions, the sounds in each section follow a random distribution, so that each section is a cloud of sound with a particular density. The change in density is the main change from one section to the next, and this density change is therefore how the listener navigates through the piece. In ST/4, there are 15 sections of different density.

These ST pieces were of the very first pieces written as the result of a computer program, written at a time where computer use was extremely rare and costly. The interesting thing about ST/4 in particular is how much Xenakis chose to deviate from his own purely mathematical process. He first threw out several sections. Next, he orchestrated the material for an ensemble of 10 musicians (for a piece called ST/10). Afterwards, he took only the string parts from ST/10, and filled in the gaps with material from the other missing instruments, according to his own taste and interest, orchestrating in personal, irrational, sometimes theatrical ways.

Cassandra Miller