Bach: Prelude and Fugue in No.1 C major, BWV 870 Analysis



Bach Prelude and Fugue No.1 in C major BWV 870 Analysis 1


Bars 1-5: Period I. Starting upon the Tonic Pedal, and ending with a Perfect Cadence in the Tonic key.

Bars 5-11: Period II. Gradually works away from the Tonic, touching G major (Bar 7), D minor (Bar 7-8), and A minor (Bar 8) before ending with a Perfect Cadence in D Minor in Bar 10, prolonged into Bar 11.

Bars 11-20: Period III. Starting from D minor, and ending in the Subdominant Major (F), touching G minor (Bar 11), D minor (12), A minor (Bars 13-14) and D minor (Bars 13-14).

Bars 20-32: Period IV. Touches G major (Bar 22), D minor (Bar 23), G minor (Bar 25), and D minor (Bar 28), before working its way back to C with Full close. Coda built on the Tonic Pedal, firmly establishing the key (Bars 32-34). Ending with a Perfect Cadence in the Tonic key.


The Figure, which first appears in its complete form in the Bass of Bar 5, is much use for Imitative work throughout the movement. It is derived from the three first semiquavers (16th notes) of the Prelude, to which an Arpeggio of four notes (similar to that seen in Bar 2) is tacked on. The figure thus made up is often divided and taken by two different parts, as may be seen in Bar 8, where the first four notes are given to the Tenor, and the completion of the figure to the Bass. Other instances occur at  Bars 11, 20, 22, 25, 28, and 29.

Sometimes the first three notes are given in a contrary motion as in Bar 31 (Bass part), and Bar 32 (Alto part).

Both similar and contrary motion are employed simultaneously in Bar 14. Throughout the movement this figure is used seven times.

Period II may be subdivided at Bar 8, where, for the moment there is a Perfect Cadence to the Relative Major (A).

Period III may be subdivided at Bar 16, where for the moment there is a Perfect Cadence to the Subdominant Major (F).

Periods I and IV are not capable of subdivision.

In Bars 20-28 is seen the transposition into the key of the Subdominant of Bars 5-14.



Bach Prelude and Fugue No.1 in C major BWV 870 Analysis 2



Bars 1-5: Subject in Alto [C major].
Bars 3-9: Tonal Answer in Treble. No Counter-subject [G major].
Bars 9-13: Subject in Bass [C major].


Bars 13-21: Episode I, modulating from C major to G, and closing in that key in Bar 22.
Bars 21-25: Subject in Alto, introduced as if in D during the cadence in G major, and proceeding thereafter in D minor [D minor].
Bars 25-29: Answer in Treble [A minor].
Bars 29-39: Episode II, modulating from A minor, through G, C and F, to C major.
Bars 39-43: Answer in Bass [C major].
Bars 43-47: Episode III, modulating from G to G.
Bars 47-51: Subject in Alto [C major].
Bars 51-55: Answer in Treble, modulating to G [C major].
Bars 55-68: Episode IV, modulating from G to C.


Bars 68-72: Subject (first limb of) reiterated in Bass in a descending sequence [C major].
Bars 72-75: Subject in Alto (first limb of) reiterated [C major].
Bars 76-79: Fragments of the Subject reiterated in similar manner in Treble [C major].
Bars 80-83: Coda.


Exposition: Bars 1-13.
Counter-exposition: None.
Counter-subject: None.
Stretti: None.
Episodes: Four.
Coda: Bars 80-83.
Dominant Pedal: Bars 50-52.
Tonic Pedal (Alto part): Bars 68-71.
Tonic Pedal (Treble part): Bars 72-75.


  1. The Fugue has a “tonal Answer, and would be styled as a “tonal” Fugue. The alteration in the Answer, for the sake of tonality, is made from the third note to the fourth. There is no Counter-subject.
  2. A summary of the four Episodes:
    1. Episode I (Bar 13) is formed from the first part of the Subject in the two upper parts, with a running Free Counterpoint, founded on the latter parts of the Subject in the Bass.
    2. Episode II (Bar 29) is in two parts only, and is formed from both parts of the Subject in the Treble, with a running Counterpoint, similar to the latter part of the Subject, in the Alto.
    3. Episode III (Bar 43) has a new figure in the two upper parts, with a running Bass, similar to that in the previous Episodes.
    4. Episode IV (Bar 55) is formed in the two upper parts from the first part of the Subject, as far as Bar 60, after which suspensions become the characteristic feature. There is a running Bass throughout.