General Advice

When encountering a piece that is too famous, we tend to overlook the fine details of the score and roughly reproduce the piece as we remember it by ear. However, by returning to basics and reading the score as if it were a first sight-reading, many discoveries can be made.

Toccata

My suggestions primarily concern the Toccata section. At the beginning, after the fermata, be sure to count the rests before starting to play the 64th notes and 32nd notes. When a fermata occurs, the beat can become uncertain, but the moment the sustained note of the fermata ends marks the beginning of the rest. While this can be a difficult judgment for the listener, the D on beat 2 is the downbeat, and C# is not the downbeat of beat 2; therefore, try to feel the beat on D. The same applies to beat 4. And the same occurs in measure 2.

Normally, C# is the leading tone of D minor, making D the tonic. Thus, when progressing from the leading tone to the tonic, D becomes a resolution, and since it is also the final note of the phrase, its volume would typically be softer than C#. However, in this case, if you absolutely want to emphasize that D is the downbeat, you might consider adding an accent to D.

In measure 4, clearly distinguish between triplets and regular 16th notes. And in this case, again emphasize that the downbeat is D, not C#. In measure 8, the note on the first beat's downbeat is G, not A.

If you want these downbeat notes to sound like downbeats, adding an accent at the beginning of the beat can help. For example, in measure 8, place an accent on the downbeat of G on beat 1, F on beat 2, E on beat 3, and D on beat 4. Apply similarly thereafter.

Fugue

For the Fugue section, it is necessary to understand which parts are tutti and which are not. The Busoni edition is recommended, as its arrangement seems quite logical.