External Spaces - The Hidden Sounds of Primes is an audio-visual composition that explores the sonic potential of the prime numbers. When displayed in the shape of a spiral, the prime numbers form a surprising and often very aesthetic pattern. The peculiarity of this spiral, which was first explored by the Polish-American mathematician Stanislaw Ulam (published in 1963) and has therefore been named "Ulam-Spiral", is that certain numbers form diagonal lines on that spiral and lie therefore, when displayed in this way, in physical proximity to each other, while they are far apart regarding their actual value. This discrepancy grows with increasing value and distance to the center of the spiral. Combining primes that are close or distant to each other results in different patterns.

In their sonification these patterns are represented by mixtures of chords and sounds of very different musical intervals through which those patterns receive high musical potential.

The purpose of this composition, with a length of approximately 9 minutes, is to give an idea of the aesthetic potential of this very special and mysterious number series.

With each repetition of this algorithmic composition occur small changes in selection and combination of the prime number pattern.