The low E in the pedal is always on, and at some point the 32' is added, and octaves are heard; for the rest, all 8' stops of all manuals coupled, tremulants all on, and at some point Prestants 8' of I and II added and later taken away, and the piece ends with the "fog" of the low pedal note.
I retitled the improv as “twilight zone” here has nothing to do with the TV series.