This Prelude is constructed mainly upon the following figure seen above.
Bars 1-12: Period I. Ending with a Perfect Cadence in the key of the Dominant, F sharp.
Bars 12-23: Period II. Through Sequence, it touches various keys, G sharp minor (Bars 16-17), F sharp major (Bar 19), before ending with a Perfect Cadence in the key of the Tonic, B.
Bars 23-36: Period III. Pointing to its Dominant, it touches G sharp minor (Bars 26-27), A sharp minor (Bar 28), D sharp minor (Bars 29-30), C sharp minor (Bar 31), before ending on the Dominant with its Pedal, F sharp.
Bars 36-46: Period IV. Dominant Pedal (Bars 35,36). Ending with Perfect Cadence in the key of the Tonic, B.
Three Themes, contrasted with each other, are used in this Prelude.
Theme I almost immediately it is stated, is taken by the second voice in contrary motion (Bar 1, Bass part).
Period II starts with a new Theme (Theme II) in the upper parts in Sequence, in the key of the Dominant, a rolling figure being meanwhile assigned to the Bass part.
Period III also starts with a new figure (Theme III) in the upper part.
Period IV reproduces with slight modification the Opening bars of the original key.
A third part is occasionally added to impart fullness to the harmony, as at Bars 11-15, 24-28 and also at 35-36.
Bars 1-4: Subject in Bass [B major].
Bars 4-5: Codetta.
Bars 5-8: Real Answer in Tenor, with Counter-subject I in Bass [F sharp major].
Bars 8-10: Codetta, modulating from F sharp to B.
Bars 10-13: Subject in Alto, with Counter-subject I in Tenor [B major].
Bars 13-14: Codetta.
Bars 14-17: Answer in Treble, with Counter-subject I Alto [F sharp major].
Bars 17-19: Codetta, modulating from F sharp to B.
Bars 19-22: Subject in Bass, with Counter-subject I in Treble [B major].
Bars 22-27: Episode I, modulating from B to F sharp.
Bars 27-30: Answer in Tenor, with Counter-subject II in Treble [F sharp major].
Bars 30-35: Episode II, modulating from F sharp to B.
Bars 35-38: Subject in Alto, with Counter-subject II (fragment of) in Tenor and in full in Bass, Bars 36-38 [B major].
Bars 38-42: Episode III, modulating from B to F sharp.
Bars 42-45: Answer in Treble, with Counter-subject II in Alto [F sharp major].
Bars 45-48: Codetta, modulating from D sharp minor to G sharp minor.
Bars 48-51: Subject in Bass, with Counter-subject II in Treble [G sharp minor].
Bars 51-53: Codetta, modulating from G sharp minor to C sharp minor.
Bars 53-56: Subject in Tenor, with Counter-subject II in Alto [C sharp minor].
Bars 56-60: Episode IV, modulating from C sharp minor to E major, and closing in that key.
Bars 60-63: Subject in Tenor, with Counter-subject II in Treble (See Remark at Bar 75) [G sharp minor].
Bars 63-75: Episode V, modulating from G sharp minor to B.
Bars 75-78: Subject in Bass. Fragments of Counter-subject Ii in Tenor, with first bar of the Subject, whereas it usually appears with the second bar [B major].
Bars 78-85: Episode VI, modulating from B to D sharp minor.
Bars 85-88: Answer in Tenor, with Counter-subject II in Alto [F sharp major].
Bars 88-93: Episode VII, modulating from F sharp to B.
Bars 93-96: Subject in Treble, with Counter-subject II in Tenor [B major].
Bars 96-104: Coda, establishing the Tonic key.
Exposition: Bars 1-17.
Counter-exposition: Bars 27-45.
Coda: Bars 96-104.
- This Fugue has a “real” Answer, and would be called a “real” Fugue.
- The Counter-subject I is never used conjointly with the Counter-subject II, and it entirely disappears from the scene of action after Bar 22; in short, it only does duty for the Exposition and for the Redundant entry (Bass part) in Bar 19.
- Counter-subject I is only employed in Double Counterpoint in the Octave.
- Counter-subject II is capable of inversion both at the Octave and Twelfth, and at Bar 36 its inversion in this latter interval appears for the first time, inverting the Treble at Bar 33.
- Summary of Episodes:
- Episode I (Bar 22) is for the most part formed of new material in four-part Florid Counterpoint, though a reminiscence of the Counter-subject I appears in the Treble of Bat 26.
- Episode II (Bar 30) is in three parts, and chiefly aims at bringing into notice the Counter-subject II (in the Bass and Treble) previous to its combination in the Twelfth at Bar 36.
- Episode III (Bar 38) is in three parts, suspensions forming one of its chief features, reminiscences of the Counter-subject II being also noticeable.
- Episode IV (Bar 56) is built upon the Counter-subject II in the Bass, with three complementary parts above.
- Episode V (Bar 63) is in three parts, and is the longest of the Episodes of this Fugue. Reminiscences of the Counter-subject II are noticeable, though the material of some of it is new.
- Episodes VI (Bar 78) and VII (Bar 88) contain reminiscences of the Counter-subject II in the Bass part, with varied Counterpoint in the upper parts.