S7.10. “Dorian” Toccata and Fugue, BWV 538, mvt. 2, (a) stretto passage (soprano imitated by bass), mm. 101–8; (b) canons: in two parts, mm. 25–28; in three parts, mm. 138–43; in four parts, mm. 211–17 (asterisks mark irregular dissonances); (c) simplified version of mm. 25–28, without the irregular dissonances