given out by the oboe, repeated first by the flute, then by the viola d'amore, and finally by the viola da gamba, above the continuo in the cantata "Tritt auf die Glaubensbahn."[107]
Certain portions of the fugue in A major, further, produce the effect of concerted music, conceived for different tone-colors, rather than that of a polyphony of like sounds, especially where broken chords occur in the counterpoint. At other times, when the pedal is silent, a trio-sonata is suggested. This does not surprise us; Bach was still preoccupied with the forms of Italian chamber music. We have noted the transformation which his preludes underwent under this influence, they now being constructed upon distinct subjects; and we have seen in the Toccata in C how Bach sought to write a work in three movements, each one of a different character and tempo, in imitation of the concertos and sonatas. Here and there again, as in this instance, we find attempts at three-part writing clearly defined;[108] not merely because the pedal remains silent, but by reason of a plainly indicated design.
Bach aligned these endeavors in definite order, classified their essentials, and embodied them in the sonatas, or rather trios, for two manuals and pedal.[109]
Play these trios upon the organ, and you will divert them from their original destination. Bach composed them for the clavecin with two manuals and pedal, between the years 1722 and 1727,[110] for the purpose, Forkel tells us, of instructing his eldest son, Wilhelm Friedemann, in organ-playing, through their use in home practice.
The structure of these sonatas is analogous to that of the six violin sonatas of Bach with clavecin accompaniment; they still lack the definite form of the modern sonata;[111] they are more, as has been said, "lyric pieces."
If Bach wrote these trios to accustom his son to the technical difficulties of the organ, perchance considering them only a set of studies, and for himself an interesting occupation by which he might profit, his motives in writing the Fantasie and Fugue in G minor[112] were, apparently, very different, and may be definitely connected with the journey which he made to Hamburg in 1720. This is an hypothesis which is sustained by a whole chain of circumstances.
First of all, Mattheson, in his treatise upon thorough-bass,[113] furnishes the ground for our premise; he cites the following fugue subject as having been given to a candidate who was undergoing an examination for an organ position:
