Since the late seventeenth century, Dietrich Buxtehude (1637-1707) has been acknowledged as one of the great organists and composers of the North German tradition. Nowadays, his free organ preludes are considered both as examples of the Stylus Phantasticus, and also as the repertoire in which he developed most of his innovations. My goal is to analyze these works, interpreting the preludes' pitch and textural organization in terms of seventeenth-century music theory, in order to incorporate an awareness of the organist's perspective, and to further the appreciation of Buxtehude's contributions to the organ tradition of his time. Most of the analyses of the preludes written during the past 34 years have focused on explicating their texture, and pitch organization in terms of eighteenth-century tonality as well as the seventeenth-century tradition of musical rhetoric. In contrast, William Porter (1986) and Geoffrey Webber (2007) have analyzed the preludes in terms of a theoretical system contemporary to Buxtehude: the psalm-tone tonalities. Their analyses also draw on Harold Powers's theory (1981) regarding the transition from psalm tones to keys, which proposes an alternative system of church tones based on the organ practice of the early seventeenth century. In my analysis of Buxtehude's free organ preludes I aim to build on these insights and study the musical content in contemporary terms, by integrating a church-tone analysis of the pitch organization with a rhetorical analysis of the texture. My findings suggest an awareness of the church tones as an organizing factor in the preludes' compositional process.