I always wanted to port AOS music to HOD by hand but I couldn't so thanks to the Double Pack ROM, you don't have too. Sappy and gba2mid couldn't detect the header for AOS in Double Pack for some reason so I found it my self and it was a success that you can copy and paste something like this, 0000 0000 0000 0000 in a location of your choice in the header. Here is the address for the header for both games in one:

USA ROM
Castlevania - Harmony of Dissonance: 22667C
Castlevania - Aria of Sorrow: A7CC40

Have fun!

Here's a video of it:
http://youtu.be/exnEpy3T77Q

I'm not so sure about that. I tested HOD music to AOS and it work fine including the SFX. I guess you have to replace the SFX with a new one by going through sappy.

Sorry for my terrible English!

Wow! I just understood on how to locate the offset to the song now.

7C21 5108

Offset 0x801512.

I need to give this person credit: http://forums.feshrine.net/index.php?showtopic=954

Here is the list:

Castlevania Double Pack (USA)

Harmony of Dissonance Location: 0022667C
00226684 - Title Screen (Part 1)
0022668C - Title Screen (Part 2)
00226694 - Name Entry 2K2
0022669C - Prologue (Maxim Kischine's Theme)
002266A4 - Successor of Fate (Juste Belmont's Theme)
002266AC - Offense and Defense
002266B4 - Approach of Deplore
002266BC - Luminous Caverns
002266C4 - Skeleton Den
002266CC - Chapel of Dissonance
002266D4 - Clock Tower
002266DC - Approach of Deplore
002266E4 - To the Center of the Demoniac Castle
002266EC - Beloved Person (Lydie Erlanger's Theme)
002266F4 - Archenemy (Loop Pattern A)
002266FC - Archenemy (Loop Pattern B)
00226704 - Archenemy (Loop Pattern C)
0022670C - Epilogue 1
00226714 - Game Over
0022671C - Incarnation of Darkness (Dracula's Theme)
00226724 - Last Battle
0022672C - Epilogue 2 (Lydie Erlanger's Theme, Variation)
00226734 - Successor of Fate (Juste Belmont's Theme, Variation)
0022673C - Dark Door
00226744 - Knight Head
0022674C - VK2K2 (Vampire Killer 2002)
00226754 - Game Over (Nes Version)
0022675C - Seller of Fine Goods (Merchant's Theme)
00226764 - Maxim Kischine's Theme
0022676C - Epilogue 2 (Lydie Erlanger's Theme, Variation)
00226774 - The Item Collection Room

Aria of Sorrow Start Location: 00A7CC38
00A7CC40 - Clock Tower
00A7CC48 - Castle Corridor
00A7CC50 - Underground Reservoir
00A7CC58 - Top Floor
00A7CC60 - Dance Hall
00A7CC68 - Inner Quarters
00A7CC70 - Study
00A7CC78 - Chapel
00A7CC80 - Floating Gardens
00A7CC88 - The Arena
00A7CC90 - Forbidden Area
00A7CC98 - Chaotic Realm
00A7CCA0 - Hammer's Shop
00A7CCA8 - Name Entry
00A7CCB0 - Game Over
00A7CCB8 - Confrontation
00A7CCC0 - Formidable Enemy
00A7CCC8 - Last Battle
00A7CCD0 - Throne Fights
00A7CCD8 - Heart of Fire
00A7CCE0 - Prologue
00A7CCE8 - Premonition
00A7CCF0 - Premonition
00A7CCF8 - Epilogue
00A7CD00 - Premonition
00A7CD08 - Credits
00A7CD0A - Black Sun
00A7CD0C - Forbidden Area(Without Sound Effect)
00A7CD0E - Prologue
00A7CD10 - Hammer's Shop
00A7CD12 - Battle of Chaos
00A7CD14 - Purifaction
00A7CD16 - Dracula's Fate
00A7CD18 - Dracula's Fate
00A7CD1A - You're Not Alone
00A7CD1C - You're Not Alone
00A7CD1E - Battle of Chaos