The present volume is an edition of medieval liturgical tropes to the most extensive chants of the Roman Mass, Gloria in excelsis Deo. Following the editions of tropes to the Agnus Dei and Sanctus by the same editor in the series Corpus Troporum, this is the third part dedicated to Ordinary tropes. It is based on 137 manuscripts dating from the ninth through the thirteenth centuries.

Volume 1 contains an introduction presenting the Gloria chant, its history and its interpretation by medieval commentators. Iversen presents the various compositional methods used by medieval compilers, who, combining ‘wandering’ verses, could vary the form of the troped chant in almost unlimited ways. The innovative aspect of this edition is to present for the reader as much material from this extensive poetic tradition while keeping faithful to the manuscript witnesses.

Thus the main part of the first volume contains the critical edition of 152 tropes and prosulas amounting to thousands of verses, in various ways and at various points inserted into the Gloria chanted in the medieval Mass.