Random Walks on Neo-Riemannian Spaces: Towards Generative Transformations

Random walks, fractional Brownian motion and stochastic processes have been used extensively by composers such as Iannis Xenakis and others, creating instantly recognizable textures. A trained ear can differentiate a uniform random walk from a Poisson process or an fBm process and random rotations. In the opera Sophocles: Antigone by one of the authors of this paper, random walks on neo- Riemannian PLR spaces were experimented with yielding mixed impressions of process music and post-romantic chromaticism. When the random walk is steered by transformational rules, special textures and harmonies emerge. We propose a new kind of parameterizable random walks, a generative system, on a space of arbitrary length chords equipped with an arbitrary distance measure steered from a customizable corpus learned by the system. The corpus provides a particular texture and harmony to the generative process. The learned neo-Riemannian spaces equipped with some distance measure provide the transformational rule base of the concatenative synthesis process.