Bars 1-14: Period I. Ending with a Perfect Cadence in the key of the Relative minor, F sharp.
Bars 14-24: Period II. Modulatory in the early part, touching B major and E major before returning to the Tonic.
Three themes are used in the construction of this Prelude. Theme I starts at once in Bar 1 in the Treble part, Theme II at Bar 1 in the Bass part, and Theme III at Bar 1 in the Middle part.
At Bars 4 and 17 Themes II and III are used above Theme I. Two other varieties are noticeable, (1) at Bar 8, where Theme I is placed in the Middle part, Theme II being above and Theme III below it; (2) at Bar 20, where Theme I is at the top, Theme II is in the Middle and Theme III at the bottom. These Themes are therefore constructed with each other according to the rules of Triple Counterpoint.
In the early part of Period II the material employed is taken from Theme III, chiefly, scale passages being placed below it, leading to the repetition of all three Themes in the original key at Bar 17.
Bars 1-2: Subject in Treble [A major].
Bars 2-3: Tonal Answer in Alto [E major].
Bars 4-5: Subject in Bass [A major].
Bars 6-7: Answer in Bass [E major].
Bars 8-9: Codetta, and Close in A.
Bars 9-10: Subject in Treble [A major].
Bars 11-12: Episode I, modulating from A to F sharp minor and Close.
Bars 13-14: Subject in Bass [F sharp minor].
Bars 16-17: Subject in Bass [E major].
Bars 17-23: Episode II, modulating from A to E, and and closing in that key, and then back to A.
Bars 23-24: Subject in Bass, with new and more rapid passage in Alto [A major].
Bars 25-26: Answer in Alto [A major].
Bars 27-28: Answer in Alto [E major].
Bars 29-31: Episode III, modulating from E, through A, to D.
Bars 31-32: Subject in Alto, and Close in D [D major].
Bars 33-34: Subject in Bass, chromatically altered [B minor].
Bars 34-39: Episode IV, modulating from B minor to F sharp minor.
Bars 39-40: Answer (altered) in Bass, and close in F sharp minor [F sharp minor].
Bars 42-43: Subject in Alto [A major].
Bars 44-45: Answer (altered) in Bass [E major].
Bars 46-48: Coda, comprising frequent imitations of the Subject.
Exposition: Bars 1-7.
Coda: Bars 46-54.
- This Fugue has a “tonal” Answer and would be called a “tonal” Fugue. The alteration in the Answer, for the sake of tonality, is made from the first note to the second.
- The Answer in the Alto (Bar 2) enters before the conclusion of the Subject in the Treble, which in the Exposition is unusual.
- An Answer appears in the Bass (Bar 6) almost immediately after the Subject in the same voice. The same occurs in the Alto (Bars 25-27).
- The Subject is only found twice in the Treble (Bars 1 and 9), after that it entirely disappears from this part.
- It has not Counter-subject.
- The Episodes are constructed from material taken from the Subject.