환상곡과 푸가 사단조, BWV 542 (Fantasia and Fugue in G minor, BWV.542)

The Great Fantasia and Fugue in G minor, BWV 542, is an organ prelude and fugue by Johann Sebastian Bach. It acquired that name to distinguish it from the earlier Little Fugue in G minor, which is shorter. This piece is not to be confused with the Prelude and Fugue in A minor, which is also for organ and also sometimes called "the Great". Bach's biographer Spitta and some later scholars think that the Fugue was improvised in 1720 during Bach's audition for an organist post at St. James' Church in Hamburg. Assuming this is correct, the theme or subject of the Fugue, a Dutch popular tune (called 'Ik ben gegroet van...'), would have been given to Bach for him to demonstrate his talents as an improviser. It has been suggested that the choice of a Dutch tune was in homage to Johann Adam Reincken, the long-serving organist at St. Catherine's Church, Hamburg, who was born in the Netherlands. During his 1720 trip to Hamburg Bach is believed to have met Reincken, whose music he had known since his teens. The Fantasia may have been composed separately during Bach's time in Köthen (1717–23).