Methods of incorporating jazz in opera range from using simple blue notes and fox-trot rhythms, to utilizing jazz instruments, to employing elaborate passages of improvisation. Current definitions of "jazz opera" do not consider variations in the genre, which, because of their evolving nature and the varied background of their composers, are diverse. This study attempts to collectively discuss these third-stream works. Jazz rhythms and harmonies first appeared in the 1920s in the works of Gershwin, Harling, Krenek, and Freeman. In 1966, Gunther Schuller was the first composer to use improvisation in an opera, which has become the primary distinguishing factor. There has since been a tremendous interest in this genre by such jazz musicians as Dave Burrell, Anthony Davis, Duke Ellington, Max Roach, Anthony Braxton, George Gruntz, and Jon Faddis.

This dissertation describes the musical and religious support of the Medici family to the Medici Chapel in Florence and the historical role of the church of San Lorenzo in the liturgical development of the period. During the later Middle Ages polyphony was allowed in the Office services only at Matins and Lauds during the Tenebrae service, the last three days of Holy Week, and at Vespers anytime. This practice continued until the end of the sixteenth century when more polyphonic motets based on the Antiphon and Responsory began to be included in the various Office hours during feast days. This practice is documented by the increased number of pieces that appear in the manuscripts. Two of the transcriptions from the church of San Lorenzo included in the appendix are selected from this later repertoire.