The monk Notker the Stammerer of St. Gall (circa 840 to 912) is primarily known as the author of the "Deeds of Charlemagne" (Gesta Caroli Magni). However, he is also the inventor of sequences, liturgical hymns where religious poetry and music converge. Although his sequences—except for the Pentecost sequence—have largely disappeared from liturgical use, they are among the treasures of the Middle Ages.