The rule given in § 325 that two successive entries should not be in the same voice does not apply to two-part fugues; for if it did, the same voice would have either subject or answer mostly all through a fugue. We shall therefore modify the rule in this case, and say that in two-part fugue "the same voice should not have subject or answer twice in succession, unless separated by an episode."
336. We have written a countersubject against the answer (bars 5 to 9), but shall be unable to make much use of it in the middle and final entries, because of the stretti; for the countersubject must evidently be discontinued when the voice that is giving it has to take up the subject or answer. But fragments of it will be seen in bars 26 and 34.
337. In the counter-exposition (bars 10 to 18) the treble which first had the subject leads with the answer, and the bass replies with the subject. The first episode (bars 18 to 21) is made from the inversion of the last three notes of the subject, treated sequentially by the treble, and imitated in the fourth below by the bass.
338. The first group of middle entries (bars 22 to 28) is led by the answer, and imitated in the octave, also by the answer, at two bars' distance. The leading voice is here able to complete the answer. The second episode is founded on the fourth bar of the subject, imitated in the fourth above; it will be remembered that the imitation in the first episode was in the fourth below. This second episode is only two bars in length.
339. In the next group of middle entries (bars 30 to 35), the subject in the bass is followed in the regular interval by the answer at one bar's distance. The third episode is a sequential treatment by the treble of an ornamented form of the countersubject in bar 8, imitated in the fifth below by the bass. The final section of the fugue contains the closest stretto (bars 40 to 45) at half a bar's distance, the answer being lengthened by the repetition in bar 43 of half a bar, to bring the piece to a satisfactory close.
340. We will now write a three-part fugue, and for the sake of variety will take the answer of the last fugue as our subject. As this answer was in the key of the tonic, it follows that the present answer will be in the key of the dominant, and will consequently be identical with the subject of the last fugue. We will write an entirely new countersubject—this time, for a change, in double counterpoint in the twelfth, and will begin the fugue with the middle voice, so as to show the countersubject in both positions in the exposition. Our plan of modulation shall be the same as in the last fugue, with middle entries in A minor and F, and each group of entries after the exposition shall contain a stretto.
