Castlevania: Aria of Sorrow - Song Randomizer

aos_song_randomizer.lua

-- Castlevania: Aria of Sorrow - Song Randomizer
-- Runs on VBA-RR v23 (DO NOT USE v24)

local serial = string.char(unpack(memory.readbyterange(0x80000ac, 4)))

local m4aSongNumStart
if (serial == "A2CJ") then
  m4aSongNumStart = 0x80d7950
elseif (serial == "A2CE") then
  m4aSongNumStart = 0x80d9378
elseif (serial == "A2CP") then
  m4aSongNumStart = 0x827cd4c
else
  error("Unsupported game " .. serial)
end

memory.registerexec(m4aSongNumStart, function()
  local song = memory.getregister("r0")

  -- BGM
  if song >= 1 and song <= 36 then
    if song ~= 15 and song ~= 27 then -- excluding oneshot songs
      memory.setregister("r0", math.random(1, 36))
    end
  end

  -- Voices
  if song >= 400 and song <= 494 then
    memory.setregister("r0", math.random(400, 494))
  end
end)