Most of the episode is simply a conversation between Dr. Arnold Fellows and Albert Brock in a sort of psychiatric center (with flashbacks to show Brock's story). Brock explains that he became overwhelmed with the constant barrage of sound from various electronic devices ("My whole day was one big listen") and eventually went on a spree to destroy them (after which he was arrested). To a degree, the baroque polyphony and rather fast allegro tempo of the Bach piece illustrate this excessive stimulation that Brock experienced.
When I re-watched the episode last week, I realized that the placement of the piece also holds some significance. It's playing outside the room where Fellows and Brock meet, so when Fellows enters and later leaves, there's a sudden transition between Bach and silence as the door closes or opens. This immediate shift between extremes further highlights the contrast between the two.
