After having composed Torso with the computer, I turned back to the analogue voltage controlled studio. I wanted to see to what extent it would be possible to use the technique of so-called tendency masking while making use of analogue equipment. With a tendency mask one controls and varies the upper and lower limits of a random generator’s output. It is a technique that is typically found in computer composition (for instance in Gottfried michael Koenig’s Projekt 2). Jo Scherpenisse designed and built special equipment to be able to apply this technique in the analogue studio.

Since the purpose of a tendency mask is to have control over a random signal, it made no sense to me to define the mask shape itself by chance. I therefore chose to design a small model that made it possible to systematically permutate the shape of the masks. This led to 25 different mask shapes that each could occur in 5 different durations. This total of 125 masks was then used to control the sound synthesis of groups A to E in the matrix below. A-1 to E-1 are transformed sound groups, for which some of the transformations’ parameters were again controlled by tendency masks (with different shapes). A-2 to E-2 are transformations of the transformed groups. The colours refer to the sections of the piece as presented in the next scheme. The density of the various sections is varied by a parameter that controls the amount of simultaneously sounding groups. The scheme does not show the overlaps between the sections.

When fully worked out this scheme results in a composition of around 45 minutes. In 1999, only 25 minutes were realised with stereo reductions of the 4-channel production material due to technical limitations.
In 2006, the full score was finally worked out in an 8-channel version based on the original 4-channel production tapes.

year: 1999–2006
duration: 45:30
tracks: 8

play an excerpt from Geoglyphs