Complex sentence: In Weimar, Bach first concentrated on the organ, composing major works for the instrument, including the', the Toccata and Fugue in D minor, BWV 565 and the Prelude and Fugue in E major, BWV 566.
Split into simpler sentences: In Weimar, Bach first concentrated on the organ, and composed major compositions for the instrument. They included the', Toccata and Fugue in D minor, BWV 565 and the Prelude and Fugue in E major, BWV 566.