either half of the authentic scale should be answered in the corresponding half of the plagal scale, and vice versâ. For instance, if the subject began with the leap between tonic and dominant, in the lower half of the authentic scale,
the answer would begin with the leap between dominant and tonic,
these being the corresponding lowest and highest notes of the lower half of the plagal scale; and conversely, if the subject began in the lower half of the plagal scale, with the leap up from dominant to tonic, or down from tonic to dominant, the answer would begin in the lower half of the authentic scale with the leap up from tonic to dominant, or down from dominant to tonic.
86. The rule to be found in nearly every work on fugue respecting tonal answer is, that if a subject leaps from tonic to dominant, either direct or through the third of the tonic, the answer must be tonal—that is to say, the tonic must be answered by the dominant, and the dominant by the tonic. This is a good rule enough, if it were only observed; but, as we shall proceed to show, the great masters, from Bach and Handel downwards, "drive a coach and four through it" continually. If we wish to conform to their practice, we shall have to modify this rule very considerably.
87. Evidently the first thing to be done is, to find out what the practice of the great masters really was in this respect. For this purpose a large number of quotations will be necessary. It may be at once admitted that in the majority of instances they conformed to the old rule; but quite enough examples will be found in which it is broken to show that they did not regard it as one of the laws of the Medes and Persians. In the examples now to be given, we shall no longer add the counterpoint that accompanies the subject, because the student will by this time have learnt how to find out where the subject ends; instead of this, we shall put the answer under the subject, in order that the two may be more easily compared.
88. We first give examples in which the old rule is strictly followed. Of these there are plenty.
J. S. Bach. Wohltemperirtes Clavier, Fugue 31.
This specimen of a simple tonal answer illustrates more than one point of some importance. The subject is here in the tonic; the
