Complex sentence: The Fugue is thought to have been improvised in 1720 during Bach's audition for an organist post at St. James' Church in Hamburg; the Fantasia may have been composed separately during his time in Köthen (1717--23).
Split into simpler sentences: The Fugue is thought to have been improvised in 1720 during Bach's audition for an organist post at St. James' Church in Hamburg. The Fantasia may have been composed separately during Bach's time in Köthen (1717--23).