This thesis uses detailed musical analysis of the eighth-mode tracts in addressing some of the still unresolved questions of chant scholarship. The first question is that of the relationship between Old Roman and Gregorian chant. Although the common origin of the two chant traditions is generally acknowledged, their subsequent relationship remains uncertain because the melodic dialects had greatly diverged by the time they were notated. Parallel analysis of these chants in the two traditions enables a deeper understanding of this relationship.
The second question is that of the relationship between oral and written modes of transmission in the ecclesiastical culture of the Middle Ages. The Mass Proper chants were introduced to Francia from Rome in the middle of the eighth century, but do not appear in manuscripts with musical notation until the late ninth century. It is possible to construct a model showing how the eighth-mode tracts may have been transmitted before notation, stabilised by the memorial prompts of the text, the form, and the melodic outlines of the genre. The closeness of the readings of these chants in the earliest manuscripts may be because there was a stable oral genre, rather than because there was an early ninth-century neumed exemplar. The Middle Ages saw a transition to a culture more dependent on writing. An investigation is made of the effect this transition had on the way the eighth-mode tracts were understood by those who performed and notated them.
The history of the eighth-mode tracts before they were written down has been the focus of much speculation, because they are generally regarded as being very old, and because they are so closely related to each other. Many scholars have argued that certain eighth-mode tracts are older, or retain more archaic elements, than others. The musical and historical evidence used in support of such chronologies is critically examined.