Map Based Trainer Battle Music

For this tutorial, we will be changing the battle music for generic trainers depending on the map the player is on.

In GetBattleBGM in pokemon.c, this is where the magic happens.

First, we need to define the region map sections constants at the top of the file:

...
#include “constants/trainers.h”
+ #include ”constants/region_map_sections.h“

Next, go to GetBattleBGM which should look like this:

 
u16 GetBattleBGM(void)
{
    if (gBattleTypeFlags & BATTLE_TYPE_KYOGRE_GROUDON)
        return MUS_VS_KYOGRE_GROUDON;
    else if (gBattleTypeFlags & BATTLE_TYPE_REGI)
        return MUS_VS_REGI;
    else if (gBattleTypeFlags & (BATTLE_TYPE_LINK | BATTLE_TYPE_x2000000))
        return MUS_VS_TRAINER;
    else if (gBattleTypeFlags & BATTLE_TYPE_TRAINER)
    {
        u8 trainerClass;
 
        if (gBattleTypeFlags & BATTLE_TYPE_FRONTIER)
            trainerClass = GetFrontierOpponentClass(gTrainerBattleOpponent_A);
        else if (gBattleTypeFlags & BATTLE_TYPE_TRAINER_HILL)
            trainerClass = TRAINER_CLASS_EXPERT;
        else
            trainerClass = gTrainers[gTrainerBattleOpponent_A].trainerClass;
 
        switch (trainerClass)
        {
        case TRAINER_CLASS_AQUA_LEADER:
        case TRAINER_CLASS_MAGMA_LEADER:
            return MUS_VS_AQUA_MAGMA_LEADER;
        case TRAINER_CLASS_TEAM_AQUA:
        case TRAINER_CLASS_TEAM_MAGMA:
        case TRAINER_CLASS_AQUA_ADMIN:
        case TRAINER_CLASS_MAGMA_ADMIN:
            return MUS_VS_AQUA_MAGMA;
        case TRAINER_CLASS_LEADER:
            return MUS_VS_GYM_LEADER;
        case TRAINER_CLASS_CHAMPION:
            return MUS_VS_CHAMPION;
        case TRAINER_CLASS_PKMN_TRAINER_3:
            if (gBattleTypeFlags & BATTLE_TYPE_FRONTIER)
                return MUS_VS_RIVAL;
            if (!StringCompare(gTrainers[gTrainerBattleOpponent_A].trainerName, gText_BattleWallyName))
                return MUS_VS_TRAINER;
            return MUS_VS_RIVAL;
        case TRAINER_CLASS_ELITE_FOUR:
            return MUS_VS_ELITE_FOUR;
        case TRAINER_CLASS_SALON_MAIDEN:
        case TRAINER_CLASS_DOME_ACE:
        case TRAINER_CLASS_PALACE_MAVEN:
        case TRAINER_CLASS_ARENA_TYCOON:
        case TRAINER_CLASS_FACTORY_HEAD:
        case TRAINER_CLASS_PIKE_QUEEN:
        case TRAINER_CLASS_PYRAMID_KING:
            return MUS_VS_FRONTIER_BRAIN;
        default:
            return MUS_VS_TRAINER;
        }
    }
    else
        return MUS_VS_WILD;
}

On default under the switch statement for trainer classes is where the normal trainer battle music plays for trainer classes that don’t have special music. It’s here that we’ll be adding in a check for the map section the player is on.

For the sake of this tutorial, we will be making trainers on Route 102 map play MUS_RG_VS_TRAINER which is the standard trainer battle music for Pokémon FireRed and LeafGreen.

Here’s how that would look:

...
- default:
-   return MUS_VS_TRAINER;
 
...
+ default:
+   if (gMapHeader.regionMapSectionId == MAPSEC_ROUTE_102)
+     return MUS_RG_VS_TRAINER;
+   else
+     return MUS_VS_TRAINER;

region_map_sections.h needs to be included because without it, we won’t be able to use MAPSEC_* defines with * replacing the map name.

If I didn’t mess anything up, that should work correctly.