The purpose of this dissertation is to investigate and document the compositional components and innovations in the compositional style of Jean-Michel Defaye as they relate to two of his works for solo trombone, Deux Danses (1953, trombone and piano) and Fluctuations (1980, trombone solo, six trombones and two percussionists.) This document investigates the circumstances surrounding the creation of each piece as well as the compositional processes of Monsieur Defaye. Jean-Michel Defaye is an important composer for his commitment to the quality and challenge of the trombone literature he creates. The importance of Deux Danses is in the fact that it was this piece that put Defaye in the international spotlight. Solo works with chamber ensemble, such as Fluctuations, must be more seriously considered for performance if the standard solo repertoire for trombone is to be further expanded. Jazz style is an integral part of both of these important works and a necessary component to fully realize the composer's intent. Monsieur Defaye has demonstrated a commitment to composing for the instrument over the long term and has a sustained interest in participating in the further development of serious literature for all brass instruments. This study will add to the limited published material on Defaye and is intended to further the cause of research into the works of this important composer.