It then goes back to V again. Bach approaches these chords using their seventh notes (it is E flat for VII, C in the right hand for v, D for VII7 and later C for V in the third beat of bar 4.).
Here we have an intensification of the sequence, with quavers in the left hand against semiquavers in the right. The harmony is simple, as we go from V to i, and then back to V in the start and in the middle of bar 5. In the end of the bar, neighbor note G natural in the bass part prepares us for the modulation in bar 6. The first chord on that bar is a V7 in the key of C ( a I7 in G).Texture becomes more complicated with a wonderful melodic sequence in the left hand and demisemiquavers in the end of each beat in the right hand. The upper part is rising to a C minor chord arpeggiation found in the beginning of bar 7 (A flat prepares us). Bach though does not develop the melody in the key of C. In the second half of bar 7, a progression of chords (V-V7-III-VIIb) in the left hand brings us back to G minor. In bar 8, both parts share the melody and a new modulation, this time in the key of D minor, is prepared. In the middle of the bar we have an augmented IIb in the key of G minor (a Vb in D minor). The C sharp and E natural show that we are in different key and the first chord in bar 9 is a first inversion of D minor. This transition between G and D (I-V), so common in this kind of music, is achieved with the sharing of the melody between the two parts, in a phrase free of complicated harmonic progression. Perhaps we could say that Bach wanted a break between heavy two-part texture or maybe just wanted to highlight the transition. It becomes really noticeable in bar 9, when after the arpeggiation of chord i (in D), another sequence begins in the lower part and the melody is constantly descending until bar 11. In the first part of the sequence in bar 9 the chord progression is ib-V7c-i-V7 and leads to a major D chord in bar 10.
