This thesis focuses on a group of keyboard pieces composed in the first half of the twentieth century entitled ‘prelude’, and explores the issue of genre, investigating the significance in the application of this generic title, and the development of the piano prelude in this period. The application of a generic title often invokes the expectation of its generic features its conventional and formal characteristics. Though the prelude is one of the oldest genres in the history of keyboard music, it has relatively few conventions, and hence, with the abandonment of its primary function the prefatory role in the nineteenth century, it has been considered an indeterminate genre. Rachmaninoff, however, asserted that a generic title should carry with it appropriate generic manifestations, which parallelled similar generic concepts in literature. This expectation of generic traits is like setting up a ‘generic contract’, offering an invitation to either conform or reform, and thus affecting its course of development. A survey of the prelude’s historical development points to six rather consistent generic conventional and formal characteristics: (i) tonality, (ii) pianistic/technical figuration, (iii) thematic treatment and formal structure, (iv) improvisatory style, (v) mood content, and (vi) brevity. Though these general characteristics may overlap with other genres, it is their collective characteristics that have contributed to the genre’s unique identity. These features form the basis for an exploration of the conformity to, or further evolution of, these characteristics in the preludes of the early twentieth century. From the substantial number of piano preludes composed in this period, selected sets, representative of the various stylistic manifestations of the period, are analysed in relation to the identified generic characteristics. The examination reveals that these preludes, though apparently diversified in style and outlook, exhibit affinity in one form or another to the generic characteristics. Each example exhibits different treatments of the generic characteristics reflective of twentieth-century developments, whilst retaining its generic identity. The prelude is thus an amalgamation of a tonal, technical and affective piece, which may be considered a combination of a tonal essay, a study/toccata, and a character piece; and collectively, a sequence of tonalities, a collection of pianistic technical studies, and a compendium of musical styles/genres in miniature.