Mega Man 4:Tutorials
I will add a few ASM tutorials that you will need for your Mega Man IV hacking experience.
Sound Initial Code while choosing the weapon
Written by Insectduel
In the memory where the ROM offset is located at x78010 to x7A00F (Bank $3C by $2000).
Change $992A and $996C to the JSR initial code to the location where the empty unused memory is. Then enter the following below.
20 XX XX JSR $XXXX ; Location to the Sound ID Code. AD 38 01 LDA $0138 60 RTS A9 2E LDA #$2E ; Sound ID to play 4C BE F6 JMP $F6BE ; Init Sound
That way the sound will always hear when you choosing the weapon menu.