Olivier Messiaen (1908–1992) was the most influential composer for the organ in the 20th century. Shaped by French tradition as well as the innovations of Debussy, Stravinsky, and Bartók, Messiaen developed a unique style that would become his signature. Using Messiaen's own analytical and aesthetic notes as a point of departure, Jon Gillock offers detailed commentary on the performance of Messiaen's 66 organ works. Gillock provides background information on the composition and premiere of each piece, a translation of Messiaen's related writings, and a systematic explanation of performance considerations. Gillock also supplies details about the organ at La Trinité in Paris, the instrument for which most of Messiaen's pieces were imagined.