I can't believe this function matches

config/SOUE01/symbols.txt

@@ -20878,7 +20878,7 @@ setButtonPressSound__20dSndSmallEffectMgr_cFP14dSoundSource_c = .text:0x8037F0F0
 playBattleHitSound__20dSndSmallEffectMgr_cFQ220dSndSmallEffectMgr_c16BattleHitSound_eP14dSoundSource_c = .text:0x8037F150; // type:function size:0x6D0
 getName__14dSoundSource_cCFv = .text:0x8037F820; // type:function size:0x8
 getSourceType__14dSoundSource_cCFv = .text:0x8037F830; // type:function size:0x8
-fn_8037F840 = .text:0x8037F840; // type:function size:0x74
+setBitsIfAdjacent__20dSndSmallEffectMgr_cFP27dSndBgmDataHarpVarSetBase_cllPUl = .text:0x8037F840; // type:function size:0x74
 __dt__35SndMgrDisposer<17dSndHarpSongMgr_c>Fv = .text:0x8037F8C0; // type:function size:0x78
 create__35SndMgrDisposer<17dSndHarpSongMgr_c>Fv = .text:0x8037F940; // type:function size:0x48
 remove__35SndMgrDisposer<17dSndHarpSongMgr_c>Fv = .text:0x8037F990; // type:function size:0x10

include/d/snd/d_snd_bgm_harp_data.h

@@ -2,6 +2,7 @@
 #define D_SND_BGM_HARP_DATA_H
 
 #include "common.h"
+#include "d/snd/d_snd_rng_mgr.h"
 
 /**
  * This file deals with the pitch of the Goddess' Harp when Link
@@ -37,6 +38,10 @@ struct dSndBgmDataHarpVar_c {
         field_0x00 |= 1;
     }
 
+    bool checkFlag() const {
+        return field_0x00 & 1;
+    }
+
     /* 0x00 */ u8 field_0x00; // flags
     /* 0x01 */ s8 field_0x01; // var
 };
@@ -61,7 +66,7 @@ public:
         mPosition = position;
     }
 
-    s32 getCount() const {
+    s32 getCount() {
         return mCount;
     }
 
@@ -69,6 +74,16 @@ public:
         return mMax;
     }
 
+    s32 getNumBitsSet() {
+        s32 numBits = 0;
+        for (int i = 0; i < getCount(); i++) {
+            if (mpVars[i].checkFlag()) {
+                numBits++;
+            }
+        }
+        return numBits;
+    }
+
     dSndBgmDataHarpVar_c *getVar(s32 idx) {
         if (idx >= getCount()) {
             return nullptr;
@@ -76,6 +91,33 @@ public:
         return &mpVars[idx];
     }
 
+    s32 getRandomIdx() {
+        return dSndRngMgr_c::GetInstance()->rndIntRange(0, getCount());
+    }
+
+    s32 getRandomIdxWithBitSet() {
+        s32 numBitsSet = getNumBitsSet();
+        s32 idx;
+        if (numBitsSet <= 0) {
+            return 0;
+        } else {
+            idx = dSndRngMgr_c::GetInstance()->rndIntRange(0, getCount());
+            while (true) {
+                if (mpVars[idx].checkFlag()) {
+                    return idx;
+                }
+                idx = dSndRngMgr_c::GetInstance()->rndIntRange(0, getCount());
+            }
+        }
+    }
+
+    s32 getVal(s32 idx) {
+        if (idx >= getCount()) {
+            return 0;
+        }
+        return mpVars[idx].field_0x01;
+    }
+
     dSndBgmDataHarpVar_c *getUnusedVar() {
         if (mCount >= mMax) {
             return nullptr;

include/d/snd/d_snd_bgm_sound.h

@@ -55,7 +55,7 @@ public:
     void onBecomeActive();
     bool isBgmBattle() const;
 
-    const dSndBgmDataHarpVarSetBase_c *getCurrentHarpVarSet();
+    dSndBgmDataHarpVarSetBase_c *getCurrentHarpVarSet();
 
     u32 getStrmPlaySamplePosition();
     u32 getWavePlaySamplePosition();

include/d/snd/d_snd_bgm_sound_harp_mgr.h

@@ -15,7 +15,7 @@ public:
 
     void setPlaySamplePosition(s32 position);
 
-    const dSndBgmDataHarpVarSetBase_c *getCurrentVarSet();
+    dSndBgmDataHarpVarSetBase_c *getCurrentVarSet();
 
     bool isLoaded() const {
         return mIsLoaded;

include/d/snd/d_snd_rng_mgr.h

@@ -10,10 +10,9 @@ class dSndRngMgr_c : public dSndRng_c {
 public:
     SND_DISPOSER_MEMBERS(dSndRngMgr_c)
 
-    u32 rndIntRange(s32 min, s32 max);
-
 public:
     dSndRngMgr_c() {}
+    u32 rndIntRange(s32 min, s32 max);
 };
 
 #endif

include/d/snd/d_snd_small_effect_mgr.h

@@ -82,6 +82,8 @@ private:
     bool isPlayingSound(u32 playerIdx, u32 soundId);
     bool isPlayingSound(u32 soundId);
 
+    void setBitsIfAdjacent(dSndBgmDataHarpVarSetBase_c *set, s32 count, s32 target, u32 *pMask);
+
     /**
      * Finds a sound handle currently playing the given sound,
      * or an idle sound handle,
@@ -100,9 +102,9 @@ private:
     /* 0x30 */ s32 mDelayedSoundTimers[NUM_DELAYED_SOUNDS];
     /* 0x38 */ u32 mTextboxAdvanceSound;
     /* 0x3C */ nw4r::snd::SoundHandle mBattleTuttiHandle;
-    /* 0x40 */ u16 field_0x40;
-    /* 0x42 */ u16 field_0x42;
-    /* 0x44 */ s32 field_0x44;
+    /* 0x40 */ s16 field_0x40;
+    /* 0x42 */ s16 field_0x42;
+    /* 0x44 */ u32 field_0x44;
 };
 
 #endif

include/d/snd/d_snd_types.h

@@ -28,6 +28,8 @@ class dSndBgmSoundHarpMgr_c;
 class dSndBgmSeqConfig;
 class dSndBgmBattleConfig;
 
+class dSndBgmDataHarpVarSetBase_c;
+
 class dSndHarpSongData_c;
 class dSndTagData;
 

src/d/snd/d_snd_bgm_sound.cpp

@@ -456,7 +456,7 @@ void dSndBgmSound_c::onBecomeActive() {
     spGlobalHarpMgr->resetPrevIdx();
 }
 
-const dSndBgmDataHarpVarSetBase_c *dSndBgmSound_c::getCurrentHarpVarSet() {
+dSndBgmDataHarpVarSetBase_c *dSndBgmSound_c::getCurrentHarpVarSet() {
     if (isRunning()) {
         return mpHarpMgr->getCurrentVarSet();
     }

src/d/snd/d_snd_bgm_sound_harp_mgr.cpp

@@ -36,6 +36,6 @@ void dSndBgmSoundHarpMgr_c::setPlaySamplePosition(s32 position) {
     }
 }
 
-const dSndBgmDataHarpVarSetBase_c *dSndBgmSoundHarpMgr_c::getCurrentVarSet() {
+dSndBgmDataHarpVarSetBase_c *dSndBgmSoundHarpMgr_c::getCurrentVarSet() {
     return mpCurrVarSet;
 }

src/d/snd/d_snd_small_effect_mgr.cpp

@@ -1,7 +1,9 @@
 #include "d/snd/d_snd_small_effect_mgr.h"
 
 #include "common.h"
+#include "d/snd/d_snd_bgm_harp_data.h"
 #include "d/snd/d_snd_bgm_mgr.h"
+#include "d/snd/d_snd_bgm_sound.h"
 #include "d/snd/d_snd_calc_pitch.h"
 #include "d/snd/d_snd_checkers.h"
 #include "d/snd/d_snd_control_player_mgr.h"
@@ -603,7 +605,141 @@ bool dSndSmallEffectMgr_c::playBattleHitSound(BattleHitSound_e type, dSoundSourc
         mBattleTuttiHandle.Stop(5);
     }
 
-    // TODO ...
+    dSndBgmSound_c *bgmSound = dSndBgmMgr_c::GetInstance()->getActiveBgmSound();
+    if (bgmSound == nullptr) {
+        return false;
+    }
 
-    return true;
+    dSndBgmDataHarpVarSetBase_c *set = bgmSound->getCurrentHarpVarSet();
+    if (set == nullptr) {
+        return false;
+    }
+
+    bool ok = playSoundInternal(soundId, &mBattleTuttiHandle);
+    if (ok) {
+        nw4r::snd::SeqSoundHandle seqHandle(&mBattleTuttiHandle);
+        if (set->getCount() <= 0) {
+            return true;
+        }
+
+        s32 count = set->getCount();
+        if (count == 1) {
+            field_0x40 = set->getVal(0);
+            field_0x42 = field_0x40;
+            for (int i = 1; i < 4; i++) {
+                seqHandle.WriteVariable(i, field_0x40);
+            }
+            return true;
+        } else {
+            s32 i2 = 0;
+            field_0x44 = 0;
+            s32 varIdx = 0;
+            u32 mask = 0;
+
+            // Pick a var 0
+            if (type == BATTLE_TUTTI_FINISH) {
+                field_0x40 = set->getVal(0);
+                varIdx = 0;
+            } else {
+                s32 numHarpBits = set->getNumBitsSet();
+
+                if (numHarpBits <= 0) {
+                    // No bits set, just try and pick a random variable
+                    // that's not equal to the one we picked before
+                    s32 pick = field_0x40;
+                    int i = 0;
+                    while (pick == field_0x40) {
+                        i++;
+                        if (i > 0x14) {
+                            break;
+                        }
+                        varIdx = set->getRandomIdx();
+                        pick = set->getVal(varIdx);
+                    }
+                    field_0x40 = pick;
+                } else if (numHarpBits == 1) {
+                    // One bit set, get the value (using a slightly convoluted method
+                    // due to inline complexity) without rejecting it when it equals
+                    // the previously picked value
+                    // TODO - unnecessary reload of count here.
+                    varIdx = set->getRandomIdxWithBitSet();
+                    field_0x40 = set->getVal(varIdx);
+                } else {
+                    // Multiple bits set, just pick a random variable with the bit set
+                    // that's not equal to the one we picked before
+                    s32 pick = field_0x40;
+                    int i = 0;
+                    while (pick == field_0x40) {
+                        i++;
+                        if (i > 0x14) {
+                            break;
+                        }
+                        varIdx = set->getRandomIdxWithBitSet();
+                        pick = set->getVal(varIdx);
+                    }
+                    field_0x40 = pick;
+                }
+            }
+            field_0x44 |= 1 << varIdx;
+            setBitsIfAdjacent(set, count, field_0x40, &mask);
+            seqHandle.WriteVariable(0, field_0x40);
+
+            // Pick a new field_0x42 -> var 1
+            u32 mask5 = 0;
+            s32 value = 0;
+            int i = 0;
+            do {
+                i++;
+                if (i > 0x14) {
+                    break;
+                }
+                u32 rndValue = set->getRandomIdx();
+                mask5 = 1 << rndValue;
+                value = set->getVal(rndValue);
+
+            } while ((mask & mask5) || value == field_0x42);
+            field_0x42 = value;
+            field_0x44 |= mask5;
+
+            setBitsIfAdjacent(set, count, field_0x42, &mask);
+            seqHandle.WriteVariable(1, field_0x42);
+
+            // Pick new vars 2 and 3
+            bool b = field_0x40 != field_0x42;
+            s32 seqVarIdx = 2;
+            for (; seqVarIdx < 4; seqVarIdx++) {
+                u32 rndValue = 0;
+                u32 mask5 = 0;
+                int i = 0;
+                do {
+                    i++;
+                    if (i > 0x14) {
+                        break;
+                    }
+                    rndValue = set->getRandomIdx();
+                    mask5 = 1 << rndValue;
+                } while ((mask & mask5) || (seqVarIdx >= 3 && !b && (field_0x44 & mask5)));
+                if (!(field_0x44 & mask5)) {
+                    b = true;
+                }
+                s32 nextVal = value = set->getVal(rndValue);
+                setBitsIfAdjacent(set, count, nextVal, &mask);
+                field_0x44 |= mask5;
+                seqHandle.WriteVariable(seqVarIdx, nextVal);
+            }
+        }
+    }
+
+    return ok;
+}
+
+void dSndSmallEffectMgr_c::setBitsIfAdjacent(
+    dSndBgmDataHarpVarSetBase_c *set, s32 count, s32 target, u32 *pMask
+) {
+    for (int i = 0; i < count; i++) {
+        s32 val = set->getVal(i);
+        if (val == target + 1 || val == target - 1) {
+            *pMask |= 1 << i;
+        }
+    }
 }