Prism (Eight Part Invention #2) WW
Michael Clarke - 1998

Both the trumpet and octaphonic tape parts of Prism are based on just 8 notes and on the unpitched sound of air blowing through the instrument. The trumpet is not so much a solo in the traditional sense as a reference point for the computer transformations for which spatial distribution is crucial. The computer acts like a prism: the trumpet recordings are broken into 8 harmonic components (partials) which are then treated independently. On one level, therefore, Prism might be thought of as a meditation on the sonority of the trumpet.

In the first section, 64 partials make up the eight note chords. At first these are grouped spatially according to the notes from which they are derived but as the section progresses, the same 64 partials re-position into more and more distant groupings, subtly transformrng the texture. In the second section, the partials derived from extended versions of one of the notes rotate around the speakers at different speeds in proportion to their frequency (higher partials rotating more quickly). In the third section the transformations become more wide-ranging and the solo trumpet develops a more sustained melodic line. Finally, against the background of the breath which inspires the trumpet, the instrument's harmonic structure is turned through 90 degrees, on to its side, and takes on a new, ethereal quality.