Johann Sebastian Bach - The Well-Tempered Clavier, Book I: Prelude and Fugue in C-sharp minor, BWV 849

The Well-Tempered Clavier is a collection of two sets of preludes and fugues in all 24 major and minor keys, composed for solo keyboard. BWV 849 is renowned for its complex five-voice fugue, considered one of Bach's most intellectually demanding contrapuntal works. The collection demonstrated the practicality of equal temperament tuning system.