No. 15 in G Major, BWV 860: Prelude

This is a technically challenging prelude. It is likely to be particularly difficult to play for learners with small hands. For this prelude, I believe the faster the tempo, the better, aiming for at least quarter note = 85. All eighth-note groups should be played staccato, leggiero, but within a sufficient dynamic range.

Now, attempting to play this prelude at a fast tempo presents various challenges. For instance, consider the left hand in measure 5. The first group of three sixteenth notes, D-C#-D, is difficult to imagine with any fingering other than 5-2-1. However, the seventh interval from D to C# is very wide, making the 5-2 fingering particularly challenging for those with small hands. Therefore, for units that pose a reach problem, one method is to assist with the right hand. This involves taking the first D with the left hand's 5th finger and playing the subsequent two notes with the right hand. The following E-C#-D is also challenging, so it is acceptable to take these two units with the right hand. Consider this approach if the evenness of your playing breaks down when attempting to play it conventionally.

The form of this prelude is very simple, with the peak point occurring in measure 11. Keep in mind that the music builds towards this point and then recedes from it.

From measure 13 onwards, the left hand becomes busy, but it is not necessarily required to play legato. Rather, play lightly with a detached touch, ensuring each note is clear, yet leggiero, with no need to connect one note to the next.

Fugue

This is a long fugue, spanning 86 measures. While there are several peak points, the build-up generally occurs more frequently in the latter half of the piece. As the piece progresses into the second half, for example, 32nd notes appear in measure 55, and long trills like those in measures 64 and 69 emerge. The climax is in measure 79, where all voices simultaneously play the subject, creating a highly tense section.

Sequences often appear in groups of three, each lasting one measure, over a three-measure span. It is crucial to apply dynamic control to ensure that these three sequences do not sound flat.

The overall tempo should be one where the later appearing 32nd notes can be heard comfortably. However, for example, the many 32nd notes in the coda could be played slightly broader, slower, and with more volume in that section alone. Playing this coda strictly in tempo can sound very mechanical and unnatural.

Let's begin the commentary from the opening. At the beginning, the eighth notes are articulated staccato, starting leggiero without being too fast. The target note in measure 2 is a quarter note C, so give this C a slight accent. Subsequently, the target note in measure 3 is E; it would be good to arrive at it with a slightly more exaggerated pause than in measure 2. In measure 5, the alto enters. In measure 11, the bass enters, and finally, all three voices are together. Measures 17, 18, and 19 present a sequence in one-measure units, which is descending. Therefore, apply a crescendo in measure 16 to lead into measure 17.

In measure 20, the inverted G-major theme enters in the alto. In measure 24, the D-major theme enters in the soprano. In measure 28, the G-major theme returns in the bass. From measure 31 until measure 38, where the next theme appears, sequences and episodes continue. The theme in measure 38 enters in E minor, so control the dynamics to allow for a natural entry into E minor, either by arriving with a crescendo or a diminuendo, according to the performer's interpretation. In the E-minor section, the soprano enters in measure 38, and the alto in measure 43, but in measure 47, the bass enters, making this a section that grows in volume. The next sequence is also descending, so apply a crescendo towards measure 47.

After the sequence spanning measures 48-50, in measure 51, the B-minor theme enters in the soprano, and in measure 52, a stretto occurs, with the theme entering in the bass. In measure 60, the D-major theme enters in the alto. This area is likely to be the dynamically largest section, so continuously build the tension.

The sequence spanning measures 65-67 will likely be the dynamically largest sequence. After concluding the theme in measure 69, the G-major theme enters in measure 77, which is also quite high in tension. Then, in measure 79, all three voices simultaneously play a single theme. In measure 82, slightly relax the tempo, and enter the coda in measure 83. As mentioned previously, this coda concludes with the overall tempo remaining relaxed.