Prelude (Toccata) and Fugue in (C or) E major, BWV 566 is an organ work written by Johann Sebastian Bach in 1708. It comprises four sections and is an early work of Bach's.
Its form resembles the Preludes and Fugues of Buxtehude. The first section alternates manual or pedal cadenzas with dense suspended chords. The second is a charming fughetta with much repetition following the circle of fifths. The third section is a brief flourish for manuals, ending with an even briefer pedal cadenza punctuated with 9-voice chords. The fourth section, in 3/4 time, is a second fugue with a rhythmic subject resembling the theme of the first fughetta.
Bach also wrote a transposed version of the piece in C major, to play on organs tuned in meantone where E major would sound discordant due to the organ's temperament. Various recordings of the C major version exist mainly on historic instruments, for example Ton Koopman's recording on the Schnitger organ in Hamburg's Jacobikirche, and Marie-Claire Alain's recording on the Silbermann organ at Freiberg Cathedral. Both have a high pitch leaving the "concert" pitch up to a tone higher than modern pitch, where the temperament is significantly unequal to merit playing it away from E major. Modern organs or those tuned to a more equal temperament do not have this need.