This study investigates the nature and extent of the relationships between the polyphonic versus of the twelfth-century Aquitanian repertory and the twelfth-century two-part conductus repertory. The versus chosen for comparison are found in the manuscripts Paris, Bibliothèque nationale, fonds latin 3719 (StM-C) and London, British Library, add. 36881 (StM-D), and the conductus are located in the seventh fascicle of the manuscript Florence, Biblioteca Medicea-Laurenziana, Pluteus 29.1 (F). Although the earliest of the twelfth-century conductus had many similarities with versus from this time, the present study demonstrates how these features changed during the second half of the twelfth century, and the way that the early conductus style began to take on some of the characteristics of the later, thirteenth-century conductus repertory. These changes demonstrate the transition that took place between twelfth-century third phase organum practice and thirteenth-century discant practice. Two groups of works from each repertory are compared: first a group of three versus and ten conductus without melismas, and then a group of four versus and eight conductus with concluding melismas. These works were chosen based on their form and text setting: note-against-note and neume-against-neume, with minimal florid setting.
Approaches to rhythmic transcription methodologies for the Aquitanian polyphonic repertory are considered in this study with a view to justifying the choice of versus editions for comparison with the conductus. Recent research in the area of conductus rhythm, particularly regarding the unsuitability of the application of modal rhythm to the texted parts of the conductus, has rendered earlier editions of conductus unsuitable for comparison in the present investigation. This study includes original transcriptions of the nineteen conductus examined in this investigation. These use unstemmed noteheads for the cum littera sections and modal rhythm to transcribe the sine littera sections of the melismatic conductus.
The versus and conductus are compared in different ways. An examination of the use of vertical intervals at cadences reveals many similarities between the two repertories. Further similarities are evident in the placement, proportions, and use of texture in melismas, although these are not the same for every work. A comparison of the use of vertical intervals in the versus and early conductus reveals that there are three different approaches to the use of the third in the early conductus repertory: first, the earliest of the conductus use thirds in the same way as the versus repertory (that is, in the manner of third phase organum); second, thirds gain increasing significance in the transitional works; third, the later works use the third as one of the most important intervals in a way analogous to the discant usage of the thirteenth-century conductus. Finally, a comparison of the meaning and use of the dividing lines in the manuscripts demonstrates that these also underwent considerable change during the second half of the twelfth century: from markers at the ends of phrases or sub-groupings within the music of the versus and earlier conductus, to markers of the ends of ordines and rests of specific duration in modal melismas.