How do spells decide which intro to play?

Okay...

So, there are 24 attack magic spells, 21 effect magic spells, 9 healing magic spells, and 27 esper spells, indexed in that order.

That means the branches are marked by the end of the black magic list...

Code:

C1/ABA6: C9 18        CMP #$18

The last black magic index is h17, or rather spell 23.

...the end of the white magic list...

Code:

C1/ABAC: C9 36        CMP #$36

The last white magic index is h35, or rather spell 53

...and then the end of the espers list...

Code:

C1/ABB2: C9 51        CMP #$51

The last esper magic index is h50, or rather spell 80

So...
That would mean, I could technically make a quick and dirty change to get the spell list to do mostly what I want.
If I change this line:

Code:

C1/ABAC: C9 36        CMP #$36  ;Replace C9 36 with C9 2D

Then Effect spells would use what the game has marked as the White Magic intro, and Healing spells would share what the game has marked as the Summon intro.  Then I could just shuffle the animations around in FF3usme.
Which solves a lot of problems, but introduces a few one.  Firstly, white magic wouldn't trigger blocking shields (which isn't a problem for me, but might be for other modders).  Second, summons would start with the white magic intro... which just replaces the previous problem with a new one, albeit a less frequent one.

...I wish I understood branches better.  I thought the command was skipping lines, but that would mean

Code:

C1/ABAE: 90 0B        BCC $ABBB       ; branch if white or effect magic (X = 2)

redirects to

Code:

C1/ABC6: 7B           TDC

Which doesn't make sense to me... shouldn't it point to the same spot the Black Magic branch does, since they're skipping over the ignore defense segment?
EDIT: Oh, it's skipping BITS, not lines!  They do point to the same place.  Neat, I learned something!

Anyway, I'm going to try it.  Even if it means White magic shares its intro with Summon magic, it'll still be nice to have the three different spell types have different starts.  Thank you.

EDIT EDIT: Just tried it and it works! Awesome.
Additionally, changing the Summon Cutoff to the end of the White Magic List ensures that they don't share the same intro.

Code:

C1/ABB2: C9 51        CMP #$51  ;Replace C9 51 with C9 36

The Espers just appear instead, which is actually pretty slick.