Emergent Formal Structures of Factor Oracle-Driven Musical Improvisations

In this article, improvisations created with the factor oracle, a commonly used data structure in machine models of musical improvisation, are shown to exhibit certain formal structures independent of the musical content. We posit that these structures are in fact emergent properties of the behavior of the factor oracle itself. An expert improviser (the first author) performed a series of improvisations with Mimi, a factor oracle-driven multimodal system for human-machine improvisation, and the formal structures of each performance was independently analyzed by the performer and an experienced music structure annotator (the second author). Quantitative assessment of the similarity between the performer's and the listener's analyses was carried out using techniques from the field of automatic structure analysis. Supported by a comparison to baseline analysis approaches, the results suggest a high level of agreement between the two sets of analyses. Drawing upon this foundation of evidence, we discuss these analyses and their relationship to common classical forms, including canon- and rondo-like forms, as well as forms based on the juxtaposition of rhythmic cells.