The poet-musician Notker Balbulus (ca. 840-912), a monk in the Swiss monastery of St. Gall, popularized sequences, poems sung during Mass following—as a sequence to—the Alleluia.
Born not far from St. Gall, Notker, or Notger, Balbulus lost his father in early childhood and was brought up by an old soldier who had served in Charlemagne's army. As a young boy, Notker went to study at St. Gall, then entered the monastery as a monk, and later became its librarian. Always interested in literature, he there found congenial poet friends and like them wrote historical, poetic, and musical works. As a historian, he collected a book of legal deeds and other official documents of his monastery, adding some occasional poems, expanded the existing book of lives of the saints, and chronicled the deeds of Charlemagne. Most of his poetic works were collected in his Liber hymnorum (ca. 860-887). Though a larger treatise on music is lost, an Epistola de musica survives.
Of these works the book of hymns is by far the most important. It contains 40 sequences for the major feasts of the year, in the order of the calendar. In the foreword Notker tells us that his poems were inspired by a liturgical book containing similar poems that was brought to St. Gall in the 850s by a priest who had fled from the Abbey of Jumièges when it was destroyed during a Norman invasion and taken refuge at St. Gall. Most of Notker's sequences are rather long poems with numerous short stanzas of unequal length. In most of the poems the first and last stanzas were sung by the full choir of monks; the other stanzas, arranged in pairs of equal length, were sung alternately by halves of the choir. In the 11th and 12th centuries all the stanza pairs of a sequence, known as double versicles, were often of similar length and rhymed.
While Notker was working on these poems, his friend Tuotilo, also a monk at St. Gall, expanded the Gregorian chant repertoire by creating shorter songs, called tropes, to be inserted in various other parts of the Mass. Through the next centuries hundreds of sequences and thousands of tropes were created, so that the Mass became increasingly cumbersome. Therefore at the last sessions of the Council of Trent in 1562-1563 the Church decided to eliminate all tropes and all but a few sequences. Thus only five sequences, sung at very special occasions, are still heard today in the Roman Catholic churches: those for Easter, Whitsunday, Corpus Christi, Seven Dolors, and the Mass for the Dead (Requiem Mass)—none of them by Notker.
Further Reading on Notker Balbulus
Information on Notker's life and work is in Gustave Reese, Music in the Middle Ages (1940), and Anselm Hughes, ed., Early Medieval Music up to 1300 (1954).