This book was published in 2003. One of the most important but least studied of medieval chant repertories is that of the Kyrie. With their Latin texts, Kyrie melodies represented musical ambitions manifested alongside of and subsequent to Gregorian chant - ambitions which achieved stylistic and formal distinction. This study illuminates those features of the early Kyrie that give it its distinctive character and set it apart not only from Gregorian chant but also from other types of medieval chant. The repertory focused on in this book is a group of 22 West Frankish sources which are believed to have originated in several Aquitanian locations. The tradition represented by these manuscripts and their repertory of Kyrie melodies can be followed across a century and a half, from 950 to 1100. The Aquitanian manuscript tradition is significant because these sources represent by far the largest group of closely inter-related musical sources from the period, and the musical notation gives reliable indication of pitch up to a century earlier than other manuscripts of the time.