We have given a fairly full description of this fine cantata in order to show our readers what is meant when it is said that Bach based his church music essentially on chorale. Most of the cantatas are constructed in the same kind of way, _i.e._ a chorale is used as the chief subject. But that Bach did not merely work on a fixed model is shown by the fact that no two of the one hundred and ninety cantatas published by the Bachgesellschaft are alike. Nothing astonishes us more than the enormous fertility of invention shown in these wonderful works, the variety of detail, and yet the unity of purpose. The one idea of the composer was the religious effect to be obtained by the highest efforts of art devoted to the service of God. Except in Germany, they are rarely heard in their proper place as part of the church service: but the mere reading through of the scores produces a most profound effect, and creates a perpetual astonishment in the reader at the enormous resources of the composer.
Bach is generally considered as the greatest composer for the organ, but his organ works, wonderful as they are, seem small in comparison with these marvellous cantatas, all different and yet all connected, as it were, by an underlying unity of purpose.
Bach took the melody of “Ein feste Burg” for one of his finest choral-vorspiele (Peters, 245, No. 22). This is a particularly interesting composition, since it is the only chorale in which we obtain any clue to Bach’s methods of registering. In Walther’s MS. are given a few indications “a 3 clav.” for three manuals. The left hand is to begin with the fagott, sixteen feet, and the right hand on the choir with the “sesquialtera.” The piece was doubtless intended for the organ at Mühlhausen which was renovated and enlarged under Bach’s directions, and which had three manuals, containing on one a sixteen feet “fagott,” and on another a combination producing a “good sesquialtera tone.” It is one of the larger choral-vorspiele, containing fifty-eight bars.
It is worth while noticing how Bach, in this, and all other choral-vorspiele, does not adhere literally to the notes of the melody, but introduces ornamental passages, or lengthens and shortens notes to serve his purpose, or introduces the subject in augmentation and diminution. This was the regular custom amongst German organists. The choral-vorspiel is, in its simplest form, merely intended to prepare the congregation for the melody that is to be sung, but instead of a mere bald playing through of the tune, as is usual in English churches, the organist was expected to use his art in elaborating it.
