Although German composer Johann Sebastian Bach entitled his work Weihnachtsoratorium (Christmas Oratorio), it is in fact closer to a cantata cycle than an oratorio. Composed and compiled for the Christmas season as celebrated in Leipzig in 1734 and early 1735, the six parts of the Christmas Oratorio were intended to be performed on the six major feast days over that 13-day period from December 25 through January 6: the "First Day of Christmas," the "Second Day of Christmas," the "Third Day of Christmas," the "Feast of the Circumcision," the "First Sunday of the New Year," and the "Feast of the Epiphany." Furthermore, each part of the work is designed to function as an independent musical unit; each part (except the second, which starts with a "Pastoral Symphony") begins and ends with choruses in the tonic key, and each part tells a separate part of the Christmas story.
However, Bach also clearly intended the music to be heard as a unified work: not only does the oratorio tell a single story based on Biblical texts, but it is musically organized around the key of D major. The musical content of the oratorio is, for the most part, drawn from three secular cantatas: Herkules auf dem Scheidewege, BWV 213; Tonet, ihr Pauken! Erschallet, Trompeten!, BWV 214; and Preisse dein Glücke, gesegnetes Sachsen, BWV 215. In addition, portions of the music were drawn from the lost St. Mark Passion, and the sixth part of the oratorio was later given an independent existence as a separate cantata (BWV 248a).
So skillful is Bach's adaptation that listeners at the time would have been unlikely to be disturbed by Bach's self-plagiarism (which was a common procedure for him anyhow). In the manner of Bach's Passions, the text of the Christmas Oratorio is drawn from the Gospel interspersed with meditations on the meaning of the Gospel texts. While scholars conjecture that these meditations were written by Bach's usual collaborator, Christian Friedrich Henrici (known as Picander), some also suspect that Bach might have written or rewritten many of them himself because Picander did not include the text of the oratorio among his collected works. A joyfully celebratory work, the Christmas Oratorio is one of the peaks in Bach's compositional oeuvre.
The story is related in recitative by an Evangelist, or narrator, thus placing the work within the long-established tradition of religious drama. However, unlike earlier oratorios and unlike Bach's own settings of the Passion story, there is virtually no dramatic dialogue, The only named characters are the Angel in Part Two and Herod in Part Six. Scored for the usual four-part vocal forces, the oratorio is given is own distinctive character through the varied orchestration featured in each section. Thus, Part One, largely a joyous celebration of Christ's birth, is adorned by brilliantly festive trumpets and timpani. The following cantata stands in complete contrast, its gentle pastoral mood reflected in scoring that includes pairs of oboes d'amore and their more rustic cousin, the oboe da caccia. Bach then gives symmetry to the first three cantatas by bringing the trumpets and timpani back for Part Three, which opens with an exultant chorus before proceeding to the arrival of the shepherds at the manger. Part Four introduces a pair of horns into the orchestra; their resplendent tones dominate an opening chorus celebrating the glory of God. Part Five, for the lesser feast of the Sunday after New Year, calls for smaller orchestral forces -- just a pair of oboes supporting the usual strings and continuo, perhaps as a counterpart to the second cantata. Finally the full majesty of trumpets and drums returns in Part 6, the topic of which is God's power over evil, here personified by Herod and his dealings with the three Magi.