This volume provides an insight into the world of the Carolingian monks and clerics who created the fascinating liturgical organism known as the Liturgy of the Hours. It recounts the creative process behind a specific part of the Gregorian Office repertoire which has not been addressed so far. By linking historical and liturgical evidence with musical analysis, the study opens new avenues for grouping manuscripts and interpreting their interrelationships. The catalogue of melodies included in this volume contains transcriptions of the post-Pentecost antiphon repertoire from 24 manuscripts across Western Europe.