The Prelude in B minor, BWV 855a, is a beautiful piano piece by Johann Sebastian Bach, originally composed as part of "The Well-Tempered Clavier" (BWV 855) Book 1 for harpsichord. However, the version most commonly played today is an arrangement by the Russian pianist Alexander Siloti.

Composition and Siloti’s Arrangement

Bach originally wrote the prelude in E minor for harpsichord. Alexander Siloti (1863–1945), a student of Franz Liszt, arranged the piece and transposed it to B minor. In doing so, he altered the structure and added romantic elements, such as expanding the left-hand accompaniment into soft, arpeggiated chords, giving the piece a more lyrical and almost dreamlike character.

Musical Characteristics

• Siloti’s version is slower and more expressive than Bach’s original.
• The piece features a gentle, flowing melody, supported by arpeggiated accompaniment.
• The harmonic progression remains typical of Bach, but Siloti’s arrangement creates an almost impressionistic sound.