Prelude and Fugue in C-sharp major, BWV 872

Prelude and Fugue in C-sharp major, BWV 872, is a keyboard composition written by Johann Sebastian Bach. It is the third prelude and fugue in the second book of The Well-Tempered Clavier, a series of 48 preludes and fugues in every major and minor key.

Prelude
The prelude is in common time and has 50 measures, built upon the characteristic arpeggios similar to the famous C major prelude from the first book of The Well-Tempered Clavier until the fugato.

The arpeggios ends at m. 25, and the fugato starts, which uses the time signature of. It has three voices.

Fugue
The fugue has three voices and 35 measures. The subject is simply made from notes from the major triad, but has mutated many times throughout the whole fugue.