is never the case in a fugue. The opening theme, known as the "subject," is always imitated; frequently also one or more of the accompanying counterpoints to the various imitations of the subject are themselves imitated, as will be seen later in this chapter; but continuous imitation of one part by another throughout the whole piece is scarcely ever met with in a fugue.[1] This is one of the most important distinctions between the two forms.
5. Another respect in which fugue differs from canon is that in the latter the imitation by the second voice must always be exact as to the name of the interval, though in many cases (as for instance in a canon in the ninth) the quality of the interval is changed (Double Counterpoint and Canon, §§ 339, 340[2]). In a very large number of fugues, on the other hand, the first imitation is not an exact copy of the subject, but requires more or less important modification, as will be explained later.
6. A third distinction between the forms which we are now comparing is that, while in a canon the first imitation may be at any interval, it must in a fugue be always at the distance of a fourth or fifth above or below the subject. This, it must be added, refers only to the commencement of a fugue; in its later developments the entries may be at other intervals.
7. Before proceeding to treat separately of the various parts of a fugue, it will be advisable to give a general description of its form, and an explanation of the names applied to the different parts. Fugues differ so much in their structural details that it is impossible to give more than a general outline here; the numerous variations will be noticed when in later chapters we treat of the various parts one by one.
8. The Subject of a Fugue is the theme announced in the first instance by any one part or voice without harmony (except in the cases mentioned in § 3), on which the whole composition is founded. By this it is not meant that the subject is to be heard continuously throughout the fugue; this would probably cause great monotony, although instances are to be met with (e.g., in the first fugue of Bach's 'Wohltemperirtes Clavier') in which the subject is rarely absent. What is intended is that the subject is to make its appearance, at more or less frequent intervals, throughout the whole of the fugue.
9. The Answer is the transposition of the subject into the key of the perfect fourth or fifth above or below the key of the subject. In an enormously large majority of cases the keys for the subject and answer will be the tonic and dominant; occasionally we find the answer in the subdominant instead
- ↑ As an exceptional instance of a fugue in which two parts are in canon throughout should be mentioned the 'Fuga canonica in Epidiapente' (i.e., in the fifth above) in Bach's 'Musikalisches Opfer.'
- ↑ The references to "Harmony," "Counterpoint," and "Double Counterpoint and Canon" throughout this work refer to the preceding volumes of this series.
