Corpus studies of post-tonal works are rare due to challenges in addressing contrasting organizational principles among individual pieces while also providing an overarching method to summarize shared formal patterns. My analysis of Debussy’s twenty-four piano preludes combines the traditional approaches of Caplin and Hepokoski and Darcy with a non-traditional inclusion of a statistical assessment to accommodate the preludes’ diverse patterns.

I describe form in Debussy’s music from a perceptual or “bottom-up” approach. Using an a posteriori perspective, I reorient the concept of structural listening to “listen for structure” beginning with musical analysis from which formal patterns are later described. This approach identifies surface-level relationships of themes and phrases and offers a vocabulary applicable to all the preludes that also extends Caplin’s description of tight-knit and loose themes adapted to Debussy’s syntax and style. I classify thematic organization with rotation forms, extending Hepokoski and Darcy’s rotational idea as accommodating any form that emphasizes return and rebeginnings.

The non-predictive nature of Debussy’s music does not permit the use of established formal templates or formal expectations in corpus analysis, so I use a statistical measurement to identify associative relationships through pairs of musical elements that tend to occur together or separately, such as an introduction and an opening homophonic texture. The resulting positive and negative associations among musical elements can function as an ad hoc set of norms or tendencies that serve as the formal backdrop against which the individual pattern of each prelude can be compared.