In the fugue in G major, No. 15 of the 'Forty-Eight,' we shall find an example of this kind between the 20th and the 31st bars; and in the 46th fugue we shall find an elaborate counter-exposition, beginning at bar 42, in which not only the subject but the countersubject is inverted.
211. It must be clearly understood that the introduction of a counter-exposition into a fugue is purely optional. The larger number of fugues do not contain one at all. We only find one in thirteen out of the 48 fugues in the 'Wohltemperirtes Clavier'; and this is probably a fair average proportion. The instructions given in this chapter will sufficiently show the student how to write a counter-exposition, if he wishes to do so.
212. With the exposition or counter-exposition the first section of a fugue ends. The construction of the middle and final sections will be treated of in the following chapters. If the student can write a really good exposition, he is already well advanced on the road to fugal composition. Let him now take the subjects in Chapter IV., and write on them a series of fourpart expositions, as he has presumably already done in three-parts. He should also write expositions on subjects of his own invention. He must try to get as much variety as possible both in his countersubjects, and in the free added parts; he should also vary his order of entry in many different ways. He must keep his expositions when he has written them, to furnish him with material for the exercises he will have to write on the next chapter.
