In January of 2017 I had the opportunity to spend several days experimenting
with Organ Acusticum, trying out various registrations that might be useful
when playing Fantasia Apocalyptica. Here's what I jotted down about some of
the most pleasing possibilities that I happened to notice.

1) Stop 166 Vox humaine is very much like the Dulzian reed of First Lutheran's
Casavant organ, with which I was familiar when writing the piece.

2) The Alpha-and-Omega sections (chapter 1 verse 8, chapter 21 verse 6,
chapter 22 verse 13) were particularly pleasant with
 Pedal 44 (Principal 16), 46 (Subbass 16)
 Solo 136 (Vibraphone 8) [right hand]
 Positiv 172 (Principal 8) [left hand]

3) For "Delphic registration" in chapters 2, 3, 18, I used
 Hauptwerk 8 (Rohrfloete 8), 11 (Floete 8) [left hand]
 Pedal 46 (Subbass 16), 48 (Gedacktbass 16), 53 (Gedackt 8)
 Positiv 178 (Flauto douce 8), 179 (Quintatoen 8)

4) For "changeringing registration" in chapters 7 and 14, I used
 Hauptwerk 4 (Principal 8), 8 (Rohrfloete 8), 10 (Octave 4)
 Pedal 41 (Untersatz 32) thru 48 (Gedacktbass 16), 62 (Floete 2)

5) For "trumpet registration" in chapters 8, 9, 11, I don't recall what I used.
(This organ has about a dozen different trumpet stops!)

6) For "smoke registration" in chapters 4, 14, 19, I used
 Hauptwerk 8, 11, 15 (Floete 8, 4, 2)
 Pedal 48  and 53 (Gedackt 16 and 8), 63 (Violine 2), 87 (I->P), 88 (II->P)
 Positiv 172 (Principal 8), 173 (Gemshorn 8), 176 (Konzertfloete 8)

7) For "Bowl registration" in chapter 16, I used
 Hauptwerk 5 (Flute harmonique 8), 8 (Rohrfloete 8)
 Pedal 46 (Subbass 16), 52 (Cello 8), 53 (Gedackt 8)
 Solo 107 (Doppelfloete 8), 112 (Floete 4), 135 (Celesta) [harp introduction]
 Recit 145 (Diapason 8), 147 (Viole de Gambe 8), 150 (Flute octaviante 4),
  151 (Dulciane 4) [left hand]
 Positiv 173 (Gemshorn 8), 174 (Unda maris 8) [right hand]

8) For the "special effects" in chapter 17, I used the following:
 A) Solo 125 (Clarinet 8)
 B) Recit 144 (Bourdon 16), 155 (Septieme harm. 1 1/7), 156 (None harm. 8/9)
 C) Positiv 175 (Salicional 8), 191 (Carillon 3fach)
 D) Hauptwerk 7 (Viola da gamba), 15 (Floete 2)
 E) Recit 149 (Cor de nuit 8)
 F) Solo 110 (Viole d'orchestre 3fach), 127 (Tremulant stark)
  
9) For "plainsong registration" in chapter 21, I used
 Hauptwerk 8 (Rohrfloete 8)
 Solo 125 (Clarinet 8)
 Positiv 173 (Gemshorn 8), 198 (IV->II)

10) For the "sacred harp" hymn in chapter 15, I used
 Hauptwerk 4 and 10 (Principal 8 and 4)
 Pedal 87 (I->P)
 Positiv 178, 182, 186 (Flutes 8, 4, 2)
 
11) Bar 62 of chapter 22 was unexpectedly beautiful when played on
 Solo 135 (Celesta 8)

12) The "little bell" in chapter 2, bar 17, was g2 on Solo 134 (Glocken 8).

13) I also used the Glocken to play B A C H in chapter 18, bar 84.