against which it is mostly employed in double counterpoint in the tenth (compare bar 3 with bars 6, 10, 21, etc.). The figure
cannot be called a countersubject because it is not contrasted with, but derived from the subject. We shall see that it forms the germ of all the episodes. In the fourth bar it is already used in imitation to make a codetta.
311. The exposition foreshadows the treatment by stretto which Bach intends; for the entry of the bass in bar 6 is half a bar sooner than its regular place. The exposition ends at the 7th bar, and the first episode is made from the figure just quoted, by close imitation, in all the voices at one crotchet's distance.
312. As the following entry of the subject (bar 10) is in E minor, we should expect the episode to modulate to that key. Bach, however, does not do this, but makes his modulation on the first notes of the subject itself. As the original keys of tonic and dominant are not quitted till after the episode, we include this in the first section of the fugue, and consider the middle section to begin in bar 10.
313. The first group of middle entries, bars 10 to 13—subject (alto), answer (treble)—is followed by the second episode, only one bar in length. We count this as an episode because it effects a modulation from B minor to A. At bar 14 the first stretto is introduced. It is for two voices only, in the fourth above, and at a distance of half a bar. It is seldom that so early a return is made to the tonic key; but it may be said here, that in fugues containing much stretto, we often find a much greater prevalence of the original keys, and less modulation, than in fugues in which there is no close imitation. Nos. 1 and 4 of the 'Wohltemperirtes Clavier' are illustrations of this.
314. In the third episode (bars 16–21) we see the figure of the second, a sequential prolongation of the first, treated by close imitation in all the voices. It leads to the second stretto (bars 21 to 23). We said in § 251 that when there were several stretti, their interest should gradually increase. We see this illustrated here. Three voices now take part in it; the treble enters one bar after the tenor, and the alto half a bar after the treble. The intervals of entry (fifth and octave) are again regular.
315. Bar 24, though not containing subject or answer, cannot be considered as episode, because it does not modulate to a fresh key, but introduces an entry which clearly belongs to the preceding group, being the regular answer to the last preceding entry—the subject in bar 22. We therefore regard bar 24 as a codetta, similar to that so often seen in an exposition.
