ABSTRACT
The so-called Vatican Organum Treatise (henceforth VT), or 'Ars organi', included in the composite manuscript Ottoboni lat. 3025 in the Biblioteca Apostolica Vaticana is believed to have been copied in northern France (or possibly England) around the middle of the thirteenth century. An earlier version of this article was presented at the Fiftieth Annual Meeting of the American Musicological Society, Philadelphia, 1984 and at the Symposium Das Ereignis 'Notre-Dame', Wolfenbüttel, 15–20 April 1985. Although the relationship of this body of musical material to Notre Dame has long been acknowledged, the nature of that relationship has been overlooked. Frieder Zaminer called VT a 'Vorstufe' of Notre Dame. In terms of the specific choice and number of progressions, significant differences between VT and the above-mentioned discant treatises occur. The third formula, a characteristic Notre Dame type with isope-riodic elements, is treated in VT in the same manner as in F, with only minor differences occurring at the very end.
