Mendelssohn's Six Preludes and Fugues, Opus 35, were written over a number of years and completed as a set in 1837. The first of the group, the Prelude and Fugue in E minor has a Prelude, marked Allegro con fuoco, with its scintillating arpeggios, written in 1837, to be paired with a Fugue written at the bedside of his dying friend August Hanstein ten years before. The fugue subject is characterized by "forbidden" intervals, tritones, augmented second, diminished fourth. There is a 'poco a poco accelerando' over the entire middle section of the fugue, leading, prepared by a dramatic cadenza, to a solemn chorale, with clear reference to the famous Luther hymn 'Ein feste Burg ist unser Gott'. After this climax the initial fuge subject returns, now turned towards E major, leading to a peaceful resolution.