The Subject

Since Bach does not follow any rigid, pre-established forms, the Presto is a little difficult to classify. Is it a fugue? A canon?

We will call the thematic material subject, even though the Presto is not necessarily a fugue. Here is the subject:

• Two motives (marked in red and blue) alternate to form the subject. We will call the red one the eighth note motive and the blue one the sixteenth note motive.
• Some notes (the last fourth of the blue motif and the first fourth of the red motif) are shared by the motifs.
• It ends with shortened versions of the red and blue motifs. Note that the motifs alternate, except at the end.
• The Presto is based on these two motifs.

Bars 16 to 25

A second voice imitates the first a perfect fifth lower. The first note should be an E, not an F#. Bach uses F# because the Passaggio ends on the dominant of E minor.

• Notice how the motifs are used as a counterpoint to each other. We have only highlighted the first, but the process is repeated throughout the Presto.
• Harmonically, after a cycle of fifths (E, A, D, G), the key of E minor is confirmed.
• It looks like a canon to the fifth rather than a fugue.

Bars 23 to 31

Two new voices enter in a lower register before the first two voices have finished:

• The voices are inverted. The upper voice now imitates the lower voice.
• Note that the first note of bar 23 is an E, not an F# as at the beginning of the Presto.
• We have written down the B (bar 24) with which the imitation should begin, but which is not to be found in the manuscript.
• Bach varies the passage so that it ends in the key of the dominant.
• If the first two voices were still singing, we could speak of a double fugue. But this is not the case.

Bars 29 to 41

Again, two voices in an even lower register enter before the previous voices have finished. We begin in the key of B (dominant of E minor), but quickly return to E minor.

• The slightly varied eighth-note motif serves to create an ascending progression from bar 35 onwards in the upper voice, while the lower voice insists on the sixteenth-note motif.
• The passage ends in E minor.

Measures 35 to 39 merit a more detailed analysis:

 

Both the upper and lower voices are the result of a simple ascending melodic progression. The C# and D# are part of the melodic scale of E minor:

By simplifying the melodic lines, the sixteenth note motive of the lower voice is similar to the eighth note motive of the upper voice. Notice the fourth interval. In the upper voice, from the first eighth note to the second; in the lower voice, from the third to the first.

By combining the voices and completing the harmony, the passage becomes more interesting:

• In every bar, we find seventh chords.
• In measure 36 we find a minor seventh chord. It is not very common to use minor seventh chords on the II degree of minor keys. Here it is very effective.
• In measure 37, the chord is a major seventh with an augmented fifth. This chord takes us nicely into the IV degree.

Bars 39 to 54

We return to E minor in measure 41. Two voices, this time in a higher register, present the subject, again in canon to the fifth:

• The B of the second voice in measure 40 should be an A, but for tonal reasons it is a B.
• From measure 45 on, we have the longest four-voice passage so far.
• We arrive at G major (relative major to E minor) at bar 54.

Bars 53 to 74

After reaching G major, we quickly modulate to E minor and the subject appears for the last time in the bass. We find a Neapolitan sixth with a major seventh and an ascending progression. A detailed harmonic analysis can be found below.

Harmonic analysis of measures 61 to 74

• Bar 63: the E major chord has an ambiguous function: it can be a major I degree or an auxiliary dominant of the IV. It resolves as a deceptive cadence (V from A minor to VI) to reach the Neapolitan sixth.
• Bar 64: Neapolitan sixth with major seventh.
• Bar 65: the bass of the Neapolitan sixth is sustained to form the seventh of the dominant chord. The same thing happens with the G in bars 66 and 67.
• Bar 69: ascending progression to conclude.
• Measures 61 through 67 are a harmonic variation of measures 10 through 12 of the Passaggio.