As you may have noticed in the C-sharp minor Prelude and Fugue from Book I, this key expresses a certain kind of sadness. This Prelude allows for a relatively free and improvisatory approach to trills and other ornaments. This Prelude modulates several times throughout the piece.

• Measure 1: C-sharp minor
• Measure 17: G-sharp minor
• Measure 27: E major
• Measure 33: F-sharp minor, etc.

Performers should vary the tone quality and dynamics according to each key, altering the 'color' of the sound.

The challenge with this Prelude lies in its tempo. Ultimately, it is acceptable to set a tempo that allows trills and other elements to be executed smoothly and without strain; however, if the tempo is too slow, the piece will lack definition and contrast. It is recommended to perform at a moderate speed that does not impede the trills. Incidentally, if you can find an audio recording of this Prelude on online videos or similar platforms, first listen to it at normal speed, then try listening at 1.5 times the speed. Next, try listening at double speed (2 times). Even at double speed, you might not feel much discomfort. What do you think?