In the late twelfth century a group of young clerics at the cathedral of Paris developed what is now known as Notre Dame organum, a collection of polyphonic settings formulated in new rhythmic notation to embellish mass and office chants. While liturgical rubrics and an eye witness give some information about the practice of this organum at Notre Dame, the only extant manuscript sources of the music were made for other institutions. The earliest surviving manuscript containing this repertoire, W1 (Wolfenbüttel, Herzog August Bibliothek, Guelf.628 Helmst.), was made on the coast of Scotland, far removed from the musical centers receiving scholarly focus today. In the early thirteenth century the new gothic cathedral of St Andrews, housing the relics of the patron and apostle to Scotland, was under construction. The polyphony of W1, especially that for Saint Andrew, would be a crowning ornament befitting the ecclesial center of Scotland. But the unique collection of polyphony for the daily Lady mass at the end of W1 reveals a different form of liturgical music practice at St Andrews. While the Notre Dame collection has received the attention of scholars and been included in editions and analyses of the Notre Dame tradition, the Marian music has been dismissed as the local invention of a less-gifted musician, despite the fact that he incoporated some of the Notre Dame organum into his own settings. Considered within the context of St Andrews, the Marian masses are an example of the role of the daily Lady mass, and its accompanying Lady chapel in establishing a local polyphonic music practice. This seminar will consider the evidence that the Marian collection in W1 is the earliest example of polyphonic music for the Lady mass, and situate it within the liturgy of St Andrews cathedral and polyphonic practice in the British Isles.