Prelude No. 17 in A-flat Major, BWV 862

The essence of this prelude lies in its vivacity. Avoid playing it excessively slowly or heavily. The author has heard live versions at quite slow tempos, which were effective in their own way, but generally, a faster tempo is easier to play. Therefore, for articulation, all eighth notes may be played staccato. The joyful character of this prelude can be understood by observing, for example, the sixteenth notes in the left hand from measure 22, or the sixteenth notes in the right hand in measure 24.

In the opening measures 1-2, a sequence-like melody appears; express the difference in tension between these two. Play measure 2 with more volume than measure 1. By measure 8, the right hand reaches a high B. From there, it gradually descends, reaching its softest point in measure 13.

Thereafter, be careful not to let the dynamics and tone quality become flat, controlling them through sequences and key changes. Incidentally, this prelude contains a challenging passage. Many learners struggle with the left hand in measures 28-29. Although it is quite difficult, the author's suggested fingerings are provided for reference.

• Measure 28: 4353 4212 1241
• Measure 29: 4353 5432 1242

Fugue

Depending on the performance, this can be a very grand fugue. Assume the theme begins on A-flat in measure 1 and consists of seven notes up to E-flat in the right hand on the first beat of measure 2. From this point on, the analysis is the author's personal interpretation. The first target is measure 10. Here, a theme appears in the tenor that makes A-flat major feel like the tonic key. The path up to this point gradually crescendos from p, but pay attention to the soprano A-flat on the fourth beat of measure 6. If you follow this A-flat descending stepwise, it leads to G F in measure 7, then E-flat in measure 8, D-flat C B in measure 9, and finally A-flat in the target measure 10. Although the line is descending, it is reasonable to consider the tension as continuously increasing.

From measure 10 onwards, the sequence descends in sixteenth notes in the right hand. The dynamic control in this area is left to the performer. The treatment of the sequence changes depending on how the performer perceives the dynamics of the F minor subject that appears in measure 13. If the F minor subject is felt to be grand, then a crescendo in measures 11-12 would be appropriate.

After the F minor subject appears, it becomes the B-flat minor subject; the performer is also entrusted with deciding which of F minor and B-flat minor has higher tension. In measure 21, a stretto of the theme can be observed.

Then, in measure 23, it returns to the major key, and this measure is likely where the volume drops the most in this fugue. This is because, from this measure onwards, the tension must gradually build towards the goal in measure 33. Before reaching measure 33, another goal is reached in measure 27, with the A-flat major theme. The dynamics here are grand. Nevertheless, the sequence from measure 30 is clearly a crescendo. And then it reaches the cadence in measure 33.

Performers often reduce the volume in measure 33. Look at the chord on the third beat. This is a vi chord, not a I. If it were a I, it might still be dynamically weak, but the impact of a vi is very significant, an unexpected chord. A forte here is perfectly acceptable. Then, in measures 34-35, slightly relax the tempo, ending ponderously and grandly.