Part I

. In the first the chorale is sung by a special chorus of sopranos, usually boys, while the two mixed choruses and the two orchestras are treated contrapuntally. In the other instance the two choruses are united in one, as are also the two orchestras, and the chorale is sung by all the sopranos, the counterpoint being assigned to the remaining three vocal parts, supported by the orchestra.--TR.]]

[Footnote 174: B.-G. v.]

A register of quite opposite effect was used to support the whole orchestra in the Reformation Cantata[175] (1717). The Luther chorale-melody is here entrusted to the sixteen-foot _Bombarde_ on the pedal, accompanied in the orchestra by the violoncello and the violone, a similar instrument.

[Footnote 175: B.-G. xviii, 10.]

In these particular instances we see that Bach departed from the general custom of omitting the reeds and mutation stops;[176] but here the organ derived from its own resources sonorities most individual in character, the accompaniment being furnished by a second instrument (the orchestra). Moreover, as W. Rust, the authorized editor of the Bach cantatas, says, "When the organ is _obbligato_ it does not present itself in a polyphonic capacity, for then it would cover up all the other instruments; but it should be treated as a solo part, like a flute or an oboe."[177]

[Footnote 176: The _organo obbligato_ was sometimes written with more delicate intentions; for example, in the alto aria with accompaniment of an _oboe da caccia_, from the cantata _Wer weiss, wie nahe mir mein Ende?_ (B.-G. v.).]

[Footnote 177: We should add here, that the organs were not of the same pitch as the other instruments, for they were tuned to chorus-pitch, a whole tone lower than the normal diapason. The organ at Weimar, on the contrary, was a minor third higher.]

With regard to Bach's orchestra, we should remember that the cantata _Die Himmel erzählen_ ("The heavens declare the glory of God") suggests the registration for the first movement of the sonata in _E_ minor. True, it will be said that Bach wrote these trios for pedal-clavecin; but their performance upon the organ, too, should not be neglected. Certain adagios, by reason of their long-sustained notes, demand an instrument capable of prolonging the tone. This first movement, in fact, is but a transcription of the _Sinfonie_ (_adagio_ and _vivace_) which serves as an overture to the cantata just mentioned. The instrumentation: _Oboe d'amore_, _Viola da gamba_, and _continuo_. These are _timbres_ to be found in all organs; we may add that the _Viola da gamba_ of the organ was one of Bach's favorite stops. It is not unwarranted to consider that in many chorales the _cantus_, placed in the tenor, was played with this register upon a separate manual, just as Bach would have given it to the violoncellos in the orchestra.

For we must take into consideration this practice of Bach's of transferring to the organ resources of the orchestra, to the orchestra those of the organ. Thus, in the Pastorale (_Hirtengesang_) of the Christmas Oratorio, Bach produces the effect of an organ whose manuals respond to each other, the one with foundation stops contrasted with the chorus of oboes upon another.

This passing from one manual to another Bach seldom indicates in his organ compositions; one piece, however, furnishes us with directions which are authentic beyond question, and extremely interesting. It is the great prelude in _E_ flat major, published in