Page:Fugue by Ebenezer Prout.djvu/101

Chap. VI.] whenever a subject is announced by an outer part, and the other voices enter in regular ascending or descending order, a moment's thought will show the student that the countersubject, if given (as is best) to the voice which has just completed the subject or answer, will always occupy the same relative position to the subject, or answer. If the treble leads, the countersubject will always be above; and if the bass leads, it will always be below. In such cases, in order to show the countersubject during the exposition in both its aspects, as an upper and lower counterpoint, we frequently find one additional entry of subject or answer by the voice that first led, while the last entering voice has the countersubject. If the middle voice leads, it is evident that we shall have the countersubject in both positions without this additional entry, as it will be below the upper part and above the lower one. In such a case, as also when there is no regular countersubject, the additional entry is not needed. What has been said in this paragraph applies equally, under the same circumstances, to fugues with more than three voices.

187. To illustrate the matter now under notice, look at the example given in § 173. Here is an exposition of a three-part fugue, which, as it stands, might be considered quite complete. Before proceeding, however, to the first episode (see Chapter VII.) Bach introduces the answer in the treble (the voice which first led) in order to let the first countersubject (which has hitherto only been heard above the subject) appear below it in the bass—the voice which has just finished the subject.

188. Very frequently in the exposition of a fugue we meet with a codetta (§ 62) either before the first entry of the answer, or between the answer and the second entry of the subject. We must now show when such a codetta is expedient, and when, it is necessary.

189. Before the first entry of the answer a codetta will be necessary in the following cases. First, if the subject begin on the tonic with an accented note (e.g., on the first beat of a bar), and also end on the tonic, and the answer be below, it is clear that, as the answer will begin on the dominant, this note being a fourth below the tonic, cannot be sounded as a harmony note against it in two-part counterpoint.

Here it would be very bad to introduce the answer against the last note of the subject; it will be necessary to add a short codetta,

thus deferring the entry of the answer till the following bar.