Only in the first line does the incisive initial figure persist a little longer in the new accompaniment than in the original solo, but on the last page it reappears and pervades the whole orchestra, even the drums thundering out its rhythm at the climax where the holding-notes of the trumpet span the torrent of harmony like a rainbow.
Deeper still is the thought that underlies the transformation of two movements of the great violin-concerto in D minor (unfortunately lost except in its splendid arrangement for clavier) into parts of the church cantata, Wir müssen durch viel Trübsal in das Reich Gottes eingehen. In both movements the violin is replaced by the organ an octave lower, the orchestral accompaniment remaining where it was. This treatment, with the addition of new and plaintive parts for wind instruments, turns the already very long and sombre first movement into an impressive idealization of the "much tribulation" that lies between us and the kingdom of heaven. The slow movement is still more solemn, and is arranged in the same way as regards the instruments; but from the first note to the last a four-part chorus sings, to the words of the title, a mass of quite new material (except for the bass and for numerous imitations of the solo-part), treated with every variety of vocal colouring and a grandeur of conception which is not dwarfed even by the Passion according to St Matthew.
4. The four short masses, the Christmas oratorio and the B minor mass, contain every variety of adaptation from earlier work. The four short masses are indeed obviously compiled for use in a church where the orchestra was small. Only four movements in the whole collection are not traceable to other extant works; all the rest comes from church cantatas. The adaptations are not always significant; no attempt, for example, is made in the G minor mass to conceal how unfit for a Kyrie eleison is the tremendous denunciatory chorus, Herr, deine Augen sehen nach dem Glauben. But the F major and G major masses are very instructive; and the A major mass, except for the damage done to the instrumentation, is a work that no one would conceive to be not original. The Kyrie is one of Bach's most individual utterances and could surely never have fitted any other text, but we should say the same of the Gloria if we did not possess the church cantata, Halt im Gedächtniss. The Gloria begins with a triumphant polyphonic chorus accompanied by a spirited symphony for strings. At the words "et in terra pax" the time changes, and two flutes softly accompany a single solemn melody in the altos.
At the "laudamus te" the material of the beginning returns, and is interrupted again by the calm slow movement, this time in another key and for another voice, at the words "adoramus te." Twice the "laudamus" and "adoramus" alternate in a finely proportioned design; at last the words "gratias agimus tibi propter magnam gloriam tuam" are set for the full chorus to the music of the slow movement, the strings join with the flutes, and this most appropriate setting of those words is finished. And yet it is quite impossible to regard this as superseding the last chorus of Halt im Gedächtniss. Not one bar or harmony of the framework differs; yet the two versions are two independent works of art. In the cantata the beginning is for instruments only; when the slow movement (here adequately scored for a flute and two oboe d' amore) begins, the basses, permanently separated from the rest of the chorus, sing "Peace be unto you." The other voices then sing the triumph of the faithful helped by the Saviour in their battle against the world.
The slow movement is, of course, set for bass alone throughout, and at the last recurrence of the allegro the bass continues to sing "Friede sei mit euch" through the rest of the chorus, as if leading the chorus of humanity through strife to the kingdom of heaven, and then the single voice of peace remains to the end. Hardly a bar of the chorus-material is on the same themes in the two versions.
The study of the sources of the Christmas oratorio will complete the evidence on which we support our estimate of Bach's methods and range of expression. It is certain that the occasional cantatas, from which all except the chorale-tune numbers and those set to words from the Bible were taken, date from shortly before the oratorio; and that Bach, being incapable of putting inferior work even into birthday odes, rescued it from oblivion by having the verses for the oratorio numbers built on the same rhythms as those of the odes in order that he might use those occasional works as a sketch (see B.-G., Jahr. xxxiv. preface). Be this as it may, the alterations are confined to details even where an aria is transposed a fourth or fifth; but the effect of them is startling. Pleasure (Wollust) sings a lovely soprano aria to allure Hercules from the paths of Virtue, to which Hercules replies indignantly with an aria in a spirited staccato style. It is no doubt a shock to our feelings to find that Wollust's aria became the Virgin's cradle-song, while Hercules's reply became the alto aria in which Zion is bidden to "prepare for the Bridegroom." But it does not warrant the inference that Bach's music lacks definite characterization: on the contrary, these two arias are the best demonstration of his profound insight into the possibilities of musical expression within his range.
It is no part of his conception of art that Wollust should be represented by a Wagnerian Venusberg-music; the obvious way to represent Pleasure was by writing pleasant music, and with Bach's ideas of pleasance the step from this to the solemn beauty of the sacred cradle-song was a mere matter of change of colour and tempo. The key is lowered from B flat to G, the strings are veiled with the tender reed tone of a group of oboe d' amore, the soprano becomes an alto whose notes are, as it were, surrounded with a nimbus by being doubled in the upper octave by a flute; and the aria becomes worthy of its new purpose, not by losing a grossness which it never possessed, but by gaining the richness which distinguishes the perfect work from the boldly executed draft.