SCHG How-to:Play different songs on different acts

(Original guide by nineko)

Everyone's hack was using different songs in different acts (think Sonic Megamix and Sonic 1 Remastered, just to name two), and I wanted to add this feature to my soniNeko as well, so I searched the forums and the wiki for a guide or something. With much surprise, I found nothing. So I tried to do it by myself, and I'm happy to say that I succeeded! Yep guys, my first ASM edit all by myself! To be honest, I had to ask Puto what bhi.s does (since I didn't know if it was involved in the music process), but that's pretty much it, ASM isn't as hard as it seems!

So here is the result of my work, to use with the ASM68K version of Hivebrain's split disassembly.

Re-organize the playlists

In the disassembly, misc\muslist1.bin is used as the "normal playlist", while misc\muslist2.bin is used when invincibility wears off. This is redundant, not to mention gay, since those playlist are identical, but muslist1.bin has an extra byte for Final Zone + a 00 to make it even. Try to put an invincibility monitor in Final Zone, and when it's done you'll get Scrap Brain music. We don't want that. Delete muslist1.bin, and make FOUR copies of muslist2.bin, named muslist1.bin to muslist4.bin . Each of them should be 6 bytes long: 81 82 83 84 85 86. Save them in this way for now, we're going to edit them later. Now the playlists have a different meaning: muslist1.bin contains the song played on the act 1 of each zone, muslist2.bin contains acts 2, etc. Muslist4.bin isn't really needed, but it will be handy. Keep on reading to find why.

Change the playlists in the ASM to reflect the new organization

Go here: <asm>MusicList: incbin misc\muslist1.bin even</syntaxhighlight>

And change it to: <asm>MusicList1: incbin misc\muslist1.bin even MusicList2: incbin misc\muslist2.bin even MusicList3: incbin misc\muslist3.bin even MusicList4: incbin misc\muslist4.bin even</syntaxhighlight>

Then go here: <asm>MusicList2: incbin misc\muslist2.bin even</syntaxhighlight>

And delete it. Of course, I'm not talking about the one I just told you to add, there is one much below (look for "Music to play after invincibility wears off").

Change the code that picks the song at the beginning of the act

We're now going to use the act byte ($FFFFFE11) to load the correct playlist. Then we'll pick the entry from the playlist according to the zone byte ($FFFFFE10). Go to Level_GetBgm. It should look like: <asm>Level_GetBgm: tst.w ($FFFFFFF0).w bmi.s loc_3946 moveq #0,d0 move.b ($FFFFFE10).w,d0 cmpi.w #$103,($FFFFFE10).w ; is level SBZ3? bne.s Level_BgmNotLZ4 ; if not, branch moveq #5,d0 ; move 5 to d0

Level_BgmNotLZ4: cmpi.w #$502,($FFFFFE10).w ; is level FZ? bne.s Level_PlayBgm ; if not, branch moveq #6,d0 ; move 6 to d0

Level_PlayBgm: lea (MusicList).l,a1 ; load music playlist move.b (a1,d0.w),d0 ; add d0 to a1 bsr.w PlaySound ; play music move.b #$34,($FFFFD080).w ; load title card object</syntaxhighlight>

Replace it with: <asm>; NineKode begins here - How to play different songs on different acts

Level_GetBgm: tst.w ($FFFFFFF0).w bmi.w loc_3946 ; change from bmi.s to bmi.w or you'll get an error moveq #0,d0 move.b ($FFFFFE10).w,d0

cmpi.b #$0,($FFFFFE11).w ; is this act 1? bne.s Level_GetBgm2 ; if not, branch lea (MusicList1).l,a1 ; load Music Playlist for Acts 1 bra.s Level_PlayBgm ; go to PlayBgm

Level_GetBgm2: cmpi.b #$1,($FFFFFE11).w ; is this act 2? bne.s Level_GetBgm3 ; if not, branch lea (MusicList2).l,a1 ; load Music Playlist for Acts 2 bra.s Level_PlayBgm ; go to PlayBgm

Level_GetBgm3: cmpi.b #$2,($FFFFFE11).w ; is this act 3? bne.s Level_GetBgm4 ; if not, branch lea (MusicList3).l,a1 ; load Music Playlist for Acts 3 bra.s Level_PlayBgm ; go to PlayBgm

Level_GetBgm4: cmpi.b #$3,($FFFFFE11).w ; is this act 4? bne.s Level_PlayBgm ; if not, branch lea (MusicList4).l,a1 ; load Music Playlist for Acts 4

Level_PlayBgm: move.b (a1,d0.w),d0 ; get d0-th entry from the playlist bsr.w PlaySound ; play music move.b #$34,($FFFFD080).w ; load title card object

NineKode ends here</syntaxhighlight>

Change the code that picks the new song when invincibility wears off

Remember, the check after the invincibility wears off is done in another section of the code. If you don't fix it, you'll get the wrong song. We just need to copy and paste the code used above, of course with different labels. So, go here: <asm>Obj01_ChkInvin: tst.b ($FFFFFE2D).w ; does Sonic have invincibility? beq.s Obj01_ChkShoes ; if not, branch tst.w $32(a0) ; check time remaining for invinciblity beq.s Obj01_ChkShoes ; if no time remains, branch subq.w #1,$32(a0) ; subtract 1 from time bne.s Obj01_ChkShoes tst.b ($FFFFF7AA).w bne.s Obj01_RmvInvin cmpi.w #$C,($FFFFFE14).w bcs.s Obj01_RmvInvin moveq #0,d0 move.b ($FFFFFE10).w,d0 cmpi.w #$103,($FFFFFE10).w ; check if level is SBZ3 bne.s Obj01_PlayMusic moveq #5,d0 ; play SBZ music

Obj01_PlayMusic: lea (MusicList2).l,a1 move.b (a1,d0.w),d0 jsr (PlaySound).l ; play normal music</syntaxhighlight>

And replace it with: <asm>; Second part of the NineKode. Play different music on different acts - after invincibility wears off

Obj01_ChkInvin: tst.b ($FFFFFE2D).w ; does Sonic have invincibility? beq.w Obj01_ChkShoes ; if not, branch ; change to beq.w tst.w $32(a0) ; check time remaining for invinciblity beq.w Obj01_ChkShoes ; if no time remains, branch ; change to beq.w subq.w #1,$32(a0) ; subtract 1 from time bne.w Obj01_ChkShoes ; change to bne.w tst.b ($FFFFF7AA).w bne.w Obj01_RmvInvin ; change to bne.w cmpi.w #$C,($FFFFFE14).w bcs.w Obj01_RmvInvin ; change to bcs.w moveq #0,d0 move.b ($FFFFFE10).w,d0

cmpi.b #$0,($FFFFFE11).w ; is this act 1? bne.s Obj01_GetBgm2 ; if not, branch lea (MusicList1).l,a1 ; load Music Playlist for Acts 1 bra.s Obj01_PlayMusic ; go to PlayMusic

Obj01_GetBgm2: cmpi.b #$1,($FFFFFE11).w ; is this act 2? bne.s Obj01_GetBgm3 ; if not, branch lea (MusicList2).l,a1 ; load Music Playlist for Acts 2 bra.s Obj01_PlayMusic ; go to PlayMusic

Obj01_GetBgm3: cmpi.b #$2,($FFFFFE11).w ; is this act 3? bne.s Obj01_GetBgm4 ; if not, branch lea (MusicList3).l,a1 ; load Music Playlist for Acts 3 bra.s Obj01_PlayMusic ; go to PlayMusic

Obj01_GetBgm4: cmpi.b #$3,($FFFFFE11).w ; is this act 4? bne.s Obj01_PlayMusic ; if not, branch lea (MusicList4).l,a1 ; load Music Playlist for Acts 4

Obj01_PlayMusic: move.b (a1,d0.w),d0 jsr (PlaySound).l ; play normal music

NineKode ends here.</syntaxhighlight>

And now you're going to get the correct music even after invincibility wears off. But there is one more instance we need to change or we're going to have problems in Labyrinth Zone after the countdown...

Change the code which picks the song after the countdown

Go here: <asm>ResumeMusic: ; XREF: Obj64_Wobble; Sonic_Water; Obj0A_ReduceAir cmpi.w #$C,($FFFFFE14).w bhi.s loc_140AC move.w #$82,d0 ; play LZ music cmpi.w #$103,($FFFFFE10).w ; check if level is 0103 (SBZ3) bne.s loc_140A6 move.w #$86,d0 ; play SBZ music

loc_140A6: jsr (PlaySound).l </syntaxhighlight>

And replace it with: <asm>ResumeMusic: ; XREF: Obj64_Wobble; Sonic_Water; Obj0A_ReduceAir cmpi.w #$C,($FFFFFE14).w

Third section of the NineKode - Play correct music after the countdown (if you breathe)

bhi.w loc_140AC ; change to bhi.w!

cmpi.b #$0,($FFFFFE11).w ; is this act 1? bne.s Air_GetBgm2 ; if not, branch lea (MusicList1).l,a1 ; load Music Playlist for Acts 1 bra.s Air_PlayMusic ; go to PlayMusic

Air_GetBgm2: cmpi.b #$1,($FFFFFE11).w ; is this act 2? bne.s Air_GetBgm3 ; if not, branch lea (MusicList2).l,a1 ; load Music Playlist for Acts 2 bra.s Air_PlayMusic ; go to PlayMusic

Air_GetBgm3: cmpi.b #$2,($FFFFFE11).w ; is this act 3? bne.s Air_GetBgm4 ; if not, branch lea (MusicList3).l,a1 ; load Music Playlist for Acts 3 bra.s Air_PlayMusic ; go to PlayMusic

Air_GetBgm4: cmpi.b #$3,($FFFFFE11).w ; is this act 4? bne.s Air_PlayMusic ; if not, branch lea (MusicList4).l,a1 ; load Music Playlist for Acts 4

Air_PlayMusic: move.b 1(a1),d0 ; load entry $1 from the playlist

loc_140A6: jsr (PlaySound).l

NineKode ends here</syntaxhighlight>

As you see the code is always the same, recycled each and every time. Now if you try to build your ROM you'll see that it works flawlessly! Well, you're still going to get the same songs, because of how we created the playlists, but if you change a byte in a playlist you'll see that it works. There is only one more small fix to do to make it perfect btw...

Fix the playlist entries for Scrap Brain 3 and Final Zone

You know that Scrap Brain 3 is actually Labyrinth 4, and Final Zone is actually Scrap Brain 3. Way to confuse people. So, hex edit muslist4.bin and change the 82 to 86. Hex edit muslist3.bin and change the 86 to 8D. Now your ROM should sound exactly as before, except that you're given the chance to pick different songs on different acts! Playlist4.bin is also useful if you plan to add acts 4 to other zones, so keep it, it's not a great waste of space.

Find 12 more songs

Good luck on that. Now that I have the code working I can't find good songs D: To add more songs for the Act 2's and 3's, go here, and to add additional music, go here.