diff --git a/src/audio.h b/src/audio.h
index f119506edc..35f9fbe8e5 100644
--- a/src/audio.h
+++ b/src/audio.h
@@ -71,6 +71,9 @@ typedef u8* WaveData;
 // converts an 8-bit volume to a 32-bit volume. only valid for vol != 0.
 #define AU_VOL_8_TO_32(vol) (((vol) << 0x18) | 0xFFFFFF)
 
+// maximum number of instrument presets for a BGM file
+#define BGM_MAX_INSTRUMNETS 0x80
+
 #define BGM_DEFAULT_TICKS_PER_BEAT 48
 
 // fixed scale for update counter to avoid precision loss of fractional frames; 1 unit = 0.001 audio frame
@@ -87,7 +90,7 @@ typedef u8* WaveData;
 // default masterTempo for BGMPlayer, derived from BGM_DEFAULT_BPM
 #define BGM_DEFAULT_TEMPO (BGM_DEFAULT_BPM * BGM_TEMPO_SCALE)
 
-// just over 100x the default tempo, seemingly chosen for to make each tick = 256 audio samples
+// just over 100x the default tempo, seemingly chosen to make each tick = 256 audio samples
 // solves (AUDIO_SAMPLES * BGM_MFRAMES_PER_MINUTE) / (BGM_DEFAULT_TICKS_PER_BEAT * x) = 256
 //   -->  (184 * 10434782) / (48 * x) = 256
 //   -->  x = (184 * 10434782) / (48 * 256)
@@ -110,6 +113,8 @@ typedef u8* WaveData;
 #define ENV_VOL_MAX     0x80    // for 7-bit volumes, 128 (1 << 7) represents full volume
 #define ENV_VOL_SHIFT   7       // Shift required to divide by 128 (normalize 7-bit volumes after a multiply)
 
+#define PRG_MAX_COUNT   0x40
+
 // Multiplies two 7-bit volume values and normalizes the result.
 #define VOL_MULT_2(a, b) ((a)*(b) >> ENV_VOL_SHIFT)
 
diff --git a/src/audio/bgm_player.c b/src/audio/bgm_player.c
index 0f1bce1332..3c8580eda3 100644
--- a/src/audio/bgm_player.c
+++ b/src/audio/bgm_player.c
@@ -757,7 +757,7 @@ void au_bgm_player_initialize(BGMPlayer* player) {
     au_bgm_reset_all_voices(player);
     player->playbackRate = 128.0f; // set to 1.0 later om...
     player->masterTempo = BGM_DEFAULT_TEMPO;
-    player->masterTempoBPM = player->masterTempo / 100;
+    player->masterTempoBPM = BGM_DEFAULT_BPM;
     player->unused_21E = 0x80;
     player->masterVolume = AU_MAX_VOLUME_8 << 24;
     player->pushSongName = 0;
@@ -1690,21 +1690,21 @@ void au_BGMCmd_F4_SubTrackRandomPan(BGMPlayer* player, BGMPlayerTrack* track) {
 void au_BGMCmd_F5_UseInstrument(BGMPlayer* player, BGMPlayerTrack* track) {
     BGMInstrumentInfo* instrument;
     s32 volume;
-    u32 voiceIndex;
+    u32 insIndex;
     u32 patch;
     u32 bank;
 
-    voiceIndex = player->seqCmdArgs.UseInstrument.index;
-    if (voiceIndex < 0x80) {
-        if (voiceIndex < player->bgmInstrumentCount) {
-            instrument = &player->instrumentsInfo[voiceIndex];
+    insIndex = player->seqCmdArgs.UseInstrument.index;
+    if (insIndex < BGM_MAX_INSTRUMNETS) {
+        if (insIndex < player->bgmInstrumentCount) {
+            instrument = &player->instrumentsInfo[insIndex];
         } else {
             instrument = &player->globals->defaultPRGEntry;
         }
     } else {
-        voiceIndex -= 0x80;
-        if (voiceIndex < 0x40) {
-            instrument = &player->globals->dataPRG[voiceIndex];
+        insIndex -= BGM_MAX_INSTRUMNETS;
+        if (insIndex < PRG_MAX_COUNT) {
+            instrument = &player->globals->dataPRG[insIndex];
         } else {
             instrument = &player->globals->defaultPRGEntry;
         }
diff --git a/src/audio/core/engine.c b/src/audio/core/engine.c
index abb3376ee4..66e9455e76 100644
--- a/src/audio/core/engine.c
+++ b/src/audio/core/engine.c
@@ -66,7 +66,7 @@ void au_engine_init(s32 outputRate) {
     globals->dataSEF = alHeapAlloc(alHeap, 1, 0x5200);
     globals->defaultInstrument = alHeapAlloc(alHeap, 1, sizeof(Instrument));
     globals->dataPER = alHeapAlloc(alHeap, 1, 6 * sizeof(PEREntry));
-    globals->dataPRG = alHeapAlloc(alHeap, 1, 64 * sizeof(BGMInstrumentInfo));
+    globals->dataPRG = alHeapAlloc(alHeap, 1, PRG_MAX_COUNT * sizeof(BGMInstrumentInfo));
     globals->musicEventQueue = alHeapAlloc(alHeap, 1, MUS_QUEUE_SIZE * sizeof(MusicEventTrigger));
     globals->outputRate = outputRate;
     au_reset_instrument(globals->defaultInstrument);
@@ -845,12 +845,12 @@ void au_load_PRG(AuGlobals* globals, s32 romAddr) {
     au_read_rom(romAddr, &header, sizeof(header));
     dataRomAddr = romAddr + sizeof(header);
     size = header.mdata.size - sizeof(header);
-    if (size > 0x200) {
-        size = 0x200;
+    if (size > PRG_MAX_COUNT * sizeof(BGMInstrumentInfo)) {
+        size = PRG_MAX_COUNT * sizeof(BGMInstrumentInfo);
     }
     au_read_rom(dataRomAddr, globals->dataPRG, size);
     numItems = size / sizeof(BGMInstrumentInfo);
-    numItemsLeft = 0x40 - numItems;
+    numItemsLeft = PRG_MAX_COUNT - numItems;
     if (numItemsLeft > 0) {
         end = &globals->dataPRG[numItems];
         au_copy_words(&globals->defaultPRGEntry, end, sizeof(BGMInstrumentInfo));