SCHG How-to:Extend Music Slots in Sonic 1
From Sonic Retro
(Original guide by Mikel)
You may notice that in the Sound Test stops on $CF, and can't go any further than $CF. So here are instructions on how to extend the Music Slots to $FF in Sonic 1.
To start go to Sound_ChkValue, if you see this line:
cmpi.b #$E4,d7 bls.s Sound_E0toE4
Add this under Sound_E0toE4:
cmpi.b #$FF,d7 bls.w Sound_E5toFF
Then, go to Sound_81to9F, and add this above Sound_81to9F:
Sound_E5toFF: jsr sub_725CA(pc) movea.l (off_719A0).l,a4 subi.b #$E5,d7 move.b (a4,d7.w),$29(a6) movea.l (Go_MusicIndex_E5toFF).l,a4 jmp Music_Continue
Then go to loc_7202C, and change it to:
loc_7202C: jsr sub_725CA(pc) movea.l (off_719A0).l,a4 subi.b #$81,d7 move.b (a4,d7.w),$29(a6) movea.l (Go_MusicIndex).l,a4 Music_Continue: lsl.w #2,d7 movea.l (a4,d7.w),a4 moveq #0,d0 move.w (a4),d0 add.l a4,d0 move.l d0,$18(a6) move.b 5(a4),d0 move.b d0,$28(a6) tst.b $2A(a6) beq.s loc_72068 move.b $29(a6),d0
Then, change:
Go_SoundTypes: dc.l SoundTypes ; XREF: Sound_Play Go_SoundD0: dc.l SoundD0Index ; XREF: Sound_D0toDF Go_MusicIndex: dc.l MusicIndex ; XREF: Sound_81to9F Go_SoundIndex: dc.l SoundIndex ; XREF: Sound_A0toCF off_719A0: dc.l byte_71A94 ; XREF: Sound_81to9F Go_PSGIndex: dc.l PSG_Index ; XREF: sub_72926
To:
align $10 Go_SoundTypes: dc.l SoundTypes ; XREF: Sound_Play Go_SoundD0: dc.l SoundD0Index ; XREF: Sound_D0toDF Go_MusicIndex: dc.l MusicIndex ; XREF: Sound_81to9F Go_MusicIndex_E5toFF: dc.l MusicIndex_E5plus ; XREF: Sound_81to9F Go_SoundIndex: dc.l SoundIndex ; XREF: Sound_A0toCF off_719A0: dc.l byte_71A94 ; XREF: Sound_81to9F Go_PSGIndex: dc.l PSG_Index ; XREF: sub_72926
Then, go to:
Music9F: incbin sound\music9F.bin even
And add the following lines under the line I posted above:
MusicIndex_E5plus:
dc.l MusicE5, MusicE6
dc.l MusicE7, MusicE8
dc.l MusicE9, MusicEA
dc.l MusicEB, MusicEC
dc.l MusicED, MusicEE
dc.l MusicEF, MusicF0
dc.l MusicF1, MusicF2
dc.l MusicF3, MusicF4
dc.l MusicF5, MusicF6
dc.l MusicF7, MusicF8
dc.l MusicF9, MusicFA
dc.l MusicFB, MusicFC
dc.l MusicFD, MusicFE
dc.l MusicFF
Then, under MusicIndex_E5toFF, add these lines:
MusicE5: incbin sound\musicE5.bin even MusicE6: incbin sound\musicE6.bin even MusicE7: incbin sound\musicE7.bin even MusicE8: incbin sound\musicE8.bin even MusicE9: incbin sound\musicE9.bin even MusicEA: incbin sound\musicEA.bin even MusicEB: incbin sound\musicEB.bin even MusicEC: incbin sound\musicEC.bin even MusicED: incbin sound\musicED.bin even MusicEE: incbin sound\musicEE.bin even MusicEF: incbin sound\musicEF.bin even MusicF0: incbin sound\musicF0.bin even MusicF1: incbin sound\musicF1.bin even MusicF2: incbin sound\musicF2.bin even MusicF3: incbin sound\musicF3.bin even MusicF4: incbin sound\musicF4.bin even MusicF5: incbin sound\musicF5.bin even MusicF6: incbin sound\musicF6.bin even MusicF7: incbin sound\musicF7.bin even MusicF8: incbin sound\musicF8.bin even MusicF9: incbin sound\musicF9.bin even MusicFA: incbin sound\musicFA.bin even MusicFB: incbin sound\musicFB.bin even MusicFC: incbin sound\musicFC.bin even MusicFD: incbin sound\musicFD.bin even MusicFE: incbin sound\musicFE.bin even MusicFF: incbin sound\musicFF.bin even
Next, we are going to extend the slots in the Sound Test, first go to LevSel_SndTest, and change:
moveq #$4F,d0 ; if sound test moves below 0, set to $4F
To:
moveq #$7F,d0 ; if sound test moves below 0, set to $7F
Then, go to LevSel_Right, and change:
cmpi.w #$50,d0
To:
cmpi.w #$80,d0
Last but not least, we are going to allow the Sound Test to read slots $E5 to $FF, so go to LevSel_NoCheat, and change:
cmpi.w #$9F,d0 ; is sound $80-$9F being played? ble.s LevSel_PlaySnd ; if yes, branch
To:
cmpi.w #$FF,d0 ; is sound $E5-$FF being played? ble.s LevSel_PlaySnd ; if yes, branch
Then, build the rom and check out your newly added tunes.
