In this article, the author presents his work Arras (1980) as an example of a structure derived from acoustic properties of harmonicity that exhibits stochastic characteristics in its perception. He discusses the stochastic process as a model for the design of a sound structure based on spectral organisation at the form-determining level, demonstrating how harmonic and inharmonic spectra can give rise to a macro-level structure of great precision and complexity while at the micro-level allowing for a wealth of unforeseen detail and interaction that is rich in dynamic interest.