related keys, but an entry in an unrelated key is occasionally possible, if such key be naturally introduced, and not (to use Mozart's immortal phrase) "pulled in by the hair of its head."
II. A middle entry may either be isolated—that is a single appearance of subject or answer in one voice; or there may be a group of entries, two or more voices in succession giving subject or answer. In the latter case it is best, except in a close stretto (see bars 44, 45, of the fugue in § 308), that the entries should be at the distance of a fourth, fifth, or octave.
III. No two successive groups of entries should have the same order of voices.
IV. No two groups of middle entries should be in the same key, nor should the same voice have subject or answer twice in succession.
326. This last rule is not always strictly observed. A remarkable exception will be seen in the 19th fugue of the 'Wohltemperirtes Clavier,' where the bass gives the subject in bar 4, and the answer immediately after in bar 6. Another example will be seen in the fourth fugue of the same work, where at bars 19 and 22 there are two consecutive entries of the subject in the tenor. The rule is, nevertheless, a good one, and the student will do well to adhere to it carefully.
327. It is not necessary that all the voices should take part in a group of middle entries. In a two-part fugue it will of course be needful, but in one with more than two voices, one at least may rest, if desired. This, in fact, is often expedient, for the sake of obtaining the contrast of thinner and fuller harmony. For an example, see No. 15 of the 'Forty-Eight,' bars 34 to 46, and 51 to 55. In the final section of a fugue, which always begins with the last return of the original key, it is imperative that all the voices be engaged, though it is not necessary that all should have subject or answer. If, however, the fugue contains stretti, it is best that all the voices take part in the final stretto, which should also be the closest.
328. We have already seen that there is no fixed number of groups of middle entries, which may vary from one or two to five or six, or even more. Neither is there any rule as to the order of voices for these middle entries, except in so far as concerns the point referred to in Rule III., § 325. It must not be forgotten that if stretti are used, their interest should always be cumulative.
329. When a pedal point (either dominant or tonic) is met with in a fugue, it is almost always in the final section. Occasionally we find a pedal earlier in a fugue, as, for instance, in No. 35 of the 'Wohltemperirtes Clavier,' and in the choral fugue, "For holy blood must be" in Schumann's 'Paradise and the Peri.' Such cases are, however, exceptional, and the student, if he wishes to use a pedal point, had better reserve it for the final section, as it is seen in the fugue in E minor in § 298. In a fugue containing stretti, the last is often made upon a pedal,
