CHAPTER VI.
THE EXPOSITION AND COUNTER-EXPOSITION.
178. If the student clearly understands how to answer a fugue subject, and how to write a good countersubject against the answer, he will be ready to commence the next stage of his work—the composition of a complete exposition of a fugue. By the exposition, as mentioned in Chapter I. (§ 11), is meant that part of the fugue during which the voices make their first entries in succession, and which extends as far as the conclusion of the subject or answer (as the case may be) by the voice that enters last. If the student has mastered the preceding chapters of this volume, and has had sufficient practice in counterpoint to be able to add free parts to two parts that are in double counterpoint with one another (Double Counterpoint, Chapter VII.), he will find that the tasks now before him will offer him but little difficulty.
179. The first question to be considered is the order in which the different voices should enter in the exposition. The subject may in the first instance be announced by any voice, but the order of the subsequent entries will largely depend upon what voice has led.
180. In order to understand this clearly, it is needful to bear in mind the fact that the answer should always be at a distance of a fourth or fifth above or below the subject. It is also necessary to remember that the compass of the alto voice is about a fourth below that of the treble; that the tenor is an octave below the treble, and the bass an octave below the alto. We are speaking here of vocal music; but the parts in an instrumental fugue are mostly treated pretty much as if they were voice parts. For the purposes of fugal answer, we group the voices in pairs, the higher pair being the treble and tenor, and the lower the alto and bass. If the student remembers the directions for transposing a given subject which are given in Counterpoint, § 53, he will be aware that a subject given in the treble must be transposed a fourth or fifth lower for the alto, an octave lower for the tenor, and an eleventh or twelfth lower for the bass.
181. If we apply this principle to the matter now under consideration, we shall see that a subject announced by one of the higher pair of voices should be answered by one of the lower pair, and vice versa. This is the usual practice of fugue
