CUSTOM MUSIC, ASM BY CONN
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Goal: load custom overworld music, without the reseting when exiting any entrance. (Original Alttp always resets it to Overworld music).


INITIAL CODE

The coding:
pc: 00/0100: jsr to pc: 00/09d5 (after your sword charge no move)
pc: 00/095d: jsl to pc 11/a200, 60 (return jsr)

pc: 11/a200
TAX ; transfer native value to X
SBC #$0F ; check if theme is in range 00-0F (overworld themes) 
BCC $04 ; continue if yes
STZ $012C ; if no, set 012c to 00 and return to game 
RTL 
LDA $008c ; check overworld
cmp #$00
BNE $0b
LDA $008a
cmp #$00
BNE $04
STZ $012C ; if you are in dungeon/cave, set 012c to 00 and return to game 
RTL 
TXA ; regain native value X transfer to A
; now a comparison starts of themes you want to have replaced, this is overworld 02, lost woods 05, kakariko 07, dark world 09, skull woods 0d. This is necessary to not replace title screen, introduction, minigame, character selection, rabbit, rain, which is not on the map!
CMP #$02 ; if overworld theme is about to play jump to $A231 and replace, if not check if it is 05 and so forth. 
BNE $03 
JMP $A243
CMP #$05 
BNE $03 
JMP $A243 
CMP #$07 
BNE $03 
JMP $A243 
CMP #$09 
BNE $03 
JMP $A243 
CMP #$0D 
BNE $03 
JMP $A243 
STZ $012C ; if it is another theme (introduction, title screen -> return to game)
RTL 
LDA $012C ; if theme is already loaded return to game (address is loaded twice)
CMP $0131 
BNE $04 
STZ $012C 
RTL 
LDX $040A ; load screen number to X
LDA $23A300,x ; select theme from table, in dependence of screen in X
STA $012C ; play theme
STA $2140 
STA $0132 
RTL 

The table at 11/a300 contains all 07 (kakariko). You simply need to replace these number by the number you like to have played.

The table beginning at 01/4343 needs to be an exact copy of the table 11/a300 to avoid a music reset everytime you switch screens.

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ADDITIONAL FIX


AD 8C 00 C9 00 D0 0B
AD 8A 00 C9 00 D0 04
9C 2C 01
6B

Load address 008C, compare to 00, if not 00 (so if 01= on overworld), branch 0B forward to code,
the same for the other, but branch only 4 bytes;
but an old 9C 2C 01 if it is 00 (so if indoors, remain as it was).

This fix implements the code only if you are in the overworld (but not indoors). It must be so.


Conn wrote:
I made a check 11/a209: ad 8c 00 c9 00 and ad 8a 00 9c 00. If both values (7e/008c and 7e/008a are 00) you are indoors.