diff --git a/.gitignore b/.gitignore
index 9f69537f7..8e5ae8b3f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,7 +15,6 @@
 *.fwjpnfont
 *.bat
 sound/**/*.bin
-src/*.s
 tools/agbcc
 *.map
 *.id0
diff --git a/Makefile b/Makefile
index 51c25f931..2109838df 100755
--- a/Makefile
+++ b/Makefile
@@ -106,10 +106,12 @@ MID_BUILDDIR = $(BUILD_DIR)/$(MID_SUBDIR)
 
 C_SOURCES   := $(wildcard src/*.c)
 ASM_SOURCES := $(wildcard asm/*.s data/*.s)
+C_ASM_SOURCES := $(wildcard src/*.s)
 
 C_OBJECTS    := $(addprefix $(BUILD_DIR)/, $(C_SOURCES:%.c=%.o))
 ASM_OBJECTS  := $(addprefix $(BUILD_DIR)/, $(ASM_SOURCES:%.s=%.o))
-ALL_OBJECTS := $(C_OBJECTS) $(ASM_OBJECTS)
+C_ASM_OBJECTS := $(addprefix $(BUILD_DIR)/, $(C_ASM_SOURCES:%.s=%.o))
+ALL_OBJECTS := $(C_OBJECTS) $(ASM_OBJECTS) $(C_ASM_OBJECTS)
 
 SUBDIRS := $(sort $(dir $(ALL_OBJECTS)))
 
@@ -233,6 +235,13 @@ $(ASM_BUILDDIR)/%.o: $(ASM_SUBDIR)/%.s
 
 $(ASM_BUILDDIR)/%.d: $(ASM_SUBDIR)/%.s
 	@$(call scaninc,$(INCLUDE_PATHS))
+	
+$(C_BUILDDIR)/%.o: $(C_SUBDIR)/%.s
+	@$(CPP) -x assembler-with-cpp $(CPPFLAGS) $< -o $(C_BUILDDIR)/$*.s
+	$(AS) $(ASFLAGS) -o $@ $(C_BUILDDIR)/$*.s
+	
+$(C_BUILDDIR)/%.d: $(C_SUBDIR)/%.s
+	@$(call scaninc,$(INCLUDE_PATHS))
 
 libagbsyscall:
 	@$(MAKE) -C libagbsyscall TOOLCHAIN=$(TOOLCHAIN)
diff --git a/include/asm/constants/m4a_constants.inc b/include/asm/constants/m4a_constants.inc
index 62ca5bb55..ab069ec7d 100644
--- a/include/asm/constants/m4a_constants.inc
+++ b/include/asm/constants/m4a_constants.inc
@@ -1,12 +1,46 @@
+#ifndef GUARD_CONSTANTS_M4A_CONSTANTS_INC
+#define GUARD_CONSTANTS_M4A_CONSTANTS_INC
+
 	.equiv ID_NUMBER, 0x68736d53
 
 	.equiv PCM_DMA_BUF_SIZE, 1584
+	.equiv MAX_DIRECTSOUND_CHANNELS, 12
+
+	.equiv C_V, 0x40
 
 	.equiv TONEDATA_TYPE_CGB, 0x07
 	.equiv TONEDATA_TYPE_FIX, 0x08
+	.equiv TONEDATA_TYPE_REV, 0x10
+	.equiv TONEDATA_TYPE_CMP, 0x20
 	.equiv TONEDATA_TYPE_SPL, 0x40 @ key split
 	.equiv TONEDATA_TYPE_RHY, 0x80 @ rhythm
 
+	.equiv TONEDATA_P_S_PAN,  0xc0
+
+	.equiv SOUND_CHANNEL_SF_START,       0x80
+	.equiv SOUND_CHANNEL_SF_STOP,        0x40
+	.equiv SOUND_CHANNEL_SF_SPECIAL,     0x20
+	.equiv SOUND_CHANNEL_SF_LOOP,        0x10
+	.equiv SOUND_CHANNEL_SF_IEC,         0x04
+	.equiv SOUND_CHANNEL_SF_ENV,         0x03
+	.equiv SOUND_CHANNEL_SF_ENV_ATTACK,  0x03
+	.equiv SOUND_CHANNEL_SF_ENV_DECAY,   0x02
+	.equiv SOUND_CHANNEL_SF_ENV_SUSTAIN, 0x01
+	.equiv SOUND_CHANNEL_SF_ENV_RELEASE, 0x00
+	.equiv SOUND_CHANNEL_SF_ON, (SOUND_CHANNEL_SF_START | SOUND_CHANNEL_SF_STOP | SOUND_CHANNEL_SF_IEC | SOUND_CHANNEL_SF_ENV)
+
+	.equiv CGB_CHANNEL_MO_PIT, 0x02
+	.equiv CGB_CHANNEL_MO_VOL, 0x01
+
+	.equiv WAVE_DATA_FLAG_LOOP, 0xC0
+
+	.equiv MPT_FLG_VOLSET, 0x01
+	.equiv MPT_FLG_VOLCHG, 0x03
+	.equiv MPT_FLG_PITSET, 0x04
+	.equiv MPT_FLG_PITCHG, 0x0C
+	.equiv MPT_FLG_START,  0x40
+	.equiv MPT_FLG_EXIST,  0x80
+
 	.macro struct_begin
 	.struct 0
 	.endm
@@ -16,6 +50,28 @@
 	.struct \name + \size
 	.endm
 
+	struct_begin
+	struct_field o_WaveData_type, 2
+	struct_field o_WaveData_d1, 1
+	struct_field o_WaveData_flags, 1
+	struct_field o_WaveData_freq, 4
+	struct_field o_WaveData_loopStart, 4
+	struct_field o_WaveData_size, 4
+	struct_field o_WaveData_data, 0
+	struct_field WaveData_size, 0
+
+	struct_begin
+	struct_field o_ToneData_type, 1
+	struct_field o_ToneData_key, 1
+	struct_field o_ToneData_length, 1
+	struct_field o_ToneData_pan_sweep, 1
+	struct_field o_ToneData_wav, 4
+	struct_field o_ToneData_attack, 1
+	struct_field o_ToneData_decay, 1
+	struct_field o_ToneData_sustain, 1
+	struct_field o_ToneData_release, 1
+	struct_field ToneData_size, 0
+
 	struct_begin
 	struct_field o_SoundInfo_ident, 4
 	struct_field o_SoundInfo_pcmDmaCounter, 1
@@ -32,8 +88,8 @@
 	struct_field o_SoundInfo_pcmFreq, 4
 	struct_field o_SoundInfo_divFreq, 4
 	struct_field o_SoundInfo_cgbChans, 4
-	struct_field o_SoundInfo_func, 4
-	struct_field o_SoundInfo_intp, 4
+	struct_field o_SoundInfo_MPlayMainHead, 4
+	struct_field o_SoundInfo_musicPlayerHead, 4
 	struct_field o_SoundInfo_CgbSound, 4
 	struct_field o_SoundInfo_CgbOscOff, 4
 	struct_field o_SoundInfo_MidiKeyToCgbFreq, 4
@@ -41,12 +97,12 @@
 	struct_field o_SoundInfo_plynote, 4
 	struct_field o_SoundInfo_ExtVolPit, 4
 	struct_field o_SoundInfo_gap2, 16
-	struct_field o_SoundInfo_chans, 768
+	struct_field o_SoundInfo_chans, MAX_DIRECTSOUND_CHANNELS * 64
 	struct_field o_SoundInfo_pcmBuffer, PCM_DMA_BUF_SIZE * 2
 	struct_field SoundInfo_size, 0
 
 	struct_begin
-	struct_field o_SoundChannel_status, 1
+	struct_field o_SoundChannel_statusFlags, 1
 	struct_field o_SoundChannel_type, 1
 	struct_field o_SoundChannel_rightVolume, 1
 	struct_field o_SoundChannel_leftVolume, 1
@@ -54,29 +110,29 @@
 	struct_field o_SoundChannel_decay, 1
 	struct_field o_SoundChannel_sustain, 1
 	struct_field o_SoundChannel_release, 1
-	struct_field o_SoundChannel_ky, 1
-	struct_field o_SoundChannel_ev, 1
-	struct_field o_SoundChannel_er, 1
-	struct_field o_SoundChannel_el, 1
-	struct_field o_SoundChannel_iev, 1
-	struct_field o_SoundChannel_iel, 1
-	struct_field o_SoundChannel_d1, 1
-	struct_field o_SoundChannel_d2, 1
-	struct_field o_SoundChannel_gt, 1
-	struct_field o_SoundChannel_mk, 1
-	struct_field o_SoundChannel_ve, 1
-	struct_field o_SoundChannel_pr, 1
-	struct_field o_SoundChannel_rp, 1
-	struct_field o_SoundChannel_d3, 3
-	struct_field o_SoundChannel_ct, 4
+	struct_field o_SoundChannel_key, 1
+	struct_field o_SoundChannel_envelopeVolume, 1
+	struct_field o_SoundChannel_envelopeVolumeRight, 1
+	struct_field o_SoundChannel_envelopeVolumeLeft, 1
+	struct_field o_SoundChannel_pseudoEchoVolume, 1
+	struct_field o_SoundChannel_pseudoEchoLength, 1
+	struct_field o_SoundChannel_dummy1, 1
+	struct_field o_SoundChannel_dummy2, 1
+	struct_field o_SoundChannel_gateTime, 1
+	struct_field o_SoundChannel_midiKey, 1
+	struct_field o_SoundChannel_velocity, 1
+	struct_field o_SoundChannel_priority, 1
+	struct_field o_SoundChannel_rhythmPan, 1
+	struct_field o_SoundChannel_dummy3, 3
+	struct_field o_SoundChannel_count, 4
 	struct_field o_SoundChannel_fw, 4
-	struct_field o_SoundChannel_freq, 4
+	struct_field o_SoundChannel_frequency, 4
 	struct_field o_SoundChannel_wav, 4
-	struct_field o_SoundChannel_cp, 4
+	struct_field o_SoundChannel_currentPointer, 4
 	struct_field o_SoundChannel_track, 4
-	struct_field o_SoundChannel_pp, 4
-	struct_field o_SoundChannel_np, 4
-	struct_field o_SoundChannel_d4, 4
+	struct_field o_SoundChannel_prevChannelPointer, 4
+	struct_field o_SoundChannel_nextChannelPointer, 4
+	struct_field o_SoundChannel_dummy4, 4
 	struct_field o_SoundChannel_xpi, 2
 	struct_field o_SoundChannel_xpc, 2
 	struct_field SoundChannel_size, 0
@@ -112,8 +168,8 @@
 	struct_field o_MusicPlayerTrack_lfoDelay, 1
 	struct_field o_MusicPlayerTrack_lfoDelayC, 1
 	struct_field o_MusicPlayerTrack_priority, 1
-	struct_field o_MusicPlayerTrack_echoVolume, 1
-	struct_field o_MusicPlayerTrack_echoLength, 1
+	struct_field o_MusicPlayerTrack_pseudoEchoVolume, 1
+	struct_field o_MusicPlayerTrack_pseudoEchoLength, 1
 	struct_field o_MusicPlayerTrack_chan, 4
 	struct_field o_MusicPlayerTrack_ToneData_type, 1
 	struct_field o_MusicPlayerTrack_ToneData_key, 1
@@ -159,41 +215,43 @@
 	struct_field MusicPlayerInfo_size, 0
 
 	struct_begin
-	struct_field o_CgbChannel_sf, 1
-	struct_field o_CgbChannel_ty, 1
+	struct_field o_CgbChannel_statusFlags, 1
+	struct_field o_CgbChannel_type, 1
 	struct_field o_CgbChannel_rightVolume, 1
 	struct_field o_CgbChannel_leftVolume, 1
-	struct_field o_CgbChannel_at, 1
-	struct_field o_CgbChannel_de, 1
-	struct_field o_CgbChannel_su, 1
-	struct_field o_CgbChannel_re, 1
-	struct_field o_CgbChannel_ky, 1
-	struct_field o_CgbChannel_ev, 1
-	struct_field o_CgbChannel_eg, 1
-	struct_field o_CgbChannel_ec, 1
-	struct_field o_CgbChannel_echoVolume, 1
-	struct_field o_CgbChannel_echoLength, 1
-	struct_field o_CgbChannel_d1, 1
-	struct_field o_CgbChannel_d2, 1
-	struct_field o_CgbChannel_gt, 1
-	struct_field o_CgbChannel_mk, 1
-	struct_field o_CgbChannel_ve, 1
-	struct_field o_CgbChannel_pr, 1
-	struct_field o_CgbChannel_rp, 1
-	struct_field o_CgbChannel_d3, 3
-	struct_field o_CgbChannel_d5, 1
-	struct_field o_CgbChannel_sg, 1
+	struct_field o_CgbChannel_attack, 1
+	struct_field o_CgbChannel_decay, 1
+	struct_field o_CgbChannel_sustain, 1
+	struct_field o_CgbChannel_release, 1
+	struct_field o_CgbChannel_key, 1
+	struct_field o_CgbChannel_envelopeVolume, 1
+	struct_field o_CgbChannel_envelopeGoal, 1
+	struct_field o_CgbChannel_envelopeCounter, 1
+	struct_field o_CgbChannel_pseudoEchoVolume, 1
+	struct_field o_CgbChannel_pseudoEchoLength, 1
+	struct_field o_CgbChannel_dummy1, 1
+	struct_field o_CgbChannel_dummy2, 1
+	struct_field o_CgbChannel_gateTime, 1
+	struct_field o_CgbChannel_midiKey, 1
+	struct_field o_CgbChannel_velocity, 1
+	struct_field o_CgbChannel_priority, 1
+	struct_field o_CgbChannel_rhythmPan, 1
+	struct_field o_CgbChannel_dummy3, 3
+	struct_field o_CgbChannel_dummy5, 1
+	struct_field o_CgbChannel_sustainGoal, 1
 	struct_field o_CgbChannel_n4, 1
 	struct_field o_CgbChannel_pan, 1
 	struct_field o_CgbChannel_panMask, 1
-	struct_field o_CgbChannel_mo, 1
-	struct_field o_CgbChannel_le, 1
-	struct_field o_CgbChannel_sw, 1
-	struct_field o_CgbChannel_fr, 4
-	struct_field o_CgbChannel_wp, 4
-	struct_field o_CgbChannel_cp, 4
-	struct_field o_CgbChannel_tp, 4
-	struct_field o_CgbChannel_pp, 4
-	struct_field o_CgbChannel_np, 4
-	struct_field o_CgbChannel_d4, 8
+	struct_field o_CgbChannel_modify, 1
+	struct_field o_CgbChannel_length, 1
+	struct_field o_CgbChannel_sweep, 1
+	struct_field o_CgbChannel_frequency, 4
+	struct_field o_CgbChannel_wavePointer, 4
+	struct_field o_CgbChannel_currentPointer, 4
+	struct_field o_CgbChannel_track, 4
+	struct_field o_CgbChannel_prevChannelPointer, 4
+	struct_field o_CgbChannel_nextChannelPointer, 4
+	struct_field o_CgbChannel_dummy4, 8
 	struct_field CgbChannel_size, 0
+
+#endif
diff --git a/ld_script.txt b/ld_script.txt
index 4b5e35bb4..4bf9d509d 100755
--- a/ld_script.txt
+++ b/ld_script.txt
@@ -347,7 +347,7 @@ SECTIONS {
         asm/ground_effect.o(.text);
         src/ground_link.o(.text);
         asm/ground_event.o(.text);
-        asm/m4a_1.o(.text);
+        src/m4a_1.o(.text);
         src/m4a.o(.text);
         *libagbsyscall.a:CpuSet.o(.text);
         *libagbsyscall.a:SoundBiasReset.o(.text);
diff --git a/asm/m4a_1.s b/src/m4a_1.s
similarity index 75%
rename from asm/m4a_1.s
rename to src/m4a_1.s
index b6fe6f95c..8a40a25c6 100644
--- a/asm/m4a_1.s
+++ b/src/m4a_1.s
@@ -48,15 +48,15 @@ SoundMain_2:
 	adds r1, r2
 SoundMain_3:
 	str r1, [sp, 0x14]
-	ldr r3, [r0, o_SoundInfo_func]
+	ldr r3, [r0, o_SoundInfo_MPlayMainHead]
 	cmp r3, 0
 	beq SoundMain_4
-	ldr r0, [r0, o_SoundInfo_intp]
-	bl call_r3
+	ldr r0, [r0, o_SoundInfo_musicPlayerHead]
+	bl call_r3_
 	ldr r0, [sp, 0x18]
 SoundMain_4:
 	ldr r3, [r0, o_SoundInfo_CgbSound]
-	bl call_r3
+	bl call_r3_
 	ldr r0, [sp, 0x18]
 	ldr r3, [r0, o_SoundInfo_pcmSamplesPerVBlank]
 	mov r8, r3
@@ -114,7 +114,7 @@ _080AE314:
 	strb r0, [r5], 0x1
 	subs r4, r4, 0x1
 	bgt _080AE314
-	add r0, pc, 0x2F
+	adr r0, _080AE386 + 1 @ plus 1 because THUMB
 	bx r0
 	.thumb
 SoundMainRAM_NoReverb:
@@ -141,7 +141,7 @@ SoundMainRAM_NoReverb_Loop:
 	stm r6!, {r0}
 	stm r5!, {r0}
 	stm r6!, {r0}
-	subs r1, 0x1
+	subs r1, 1
 	bgt SoundMainRAM_NoReverb_Loop
 _080AE386:
 	ldr r4, [sp, 0x18]
@@ -162,77 +162,77 @@ SoundMainRAM_ChanLoop:
 	adds r1, TOTAL_SCANLINES
 _080AE3A4:
 	cmp r1, r0
-	bcc _080AE3B0
+	blo _080AE3B0
 	b _080AE682
 
 	.pool
 
 _080AE3B0:
-	ldrb r6, [r4, o_SoundChannel_status]
-	movs r0, 0xC7
+	ldrb r6, [r4, o_SoundChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r6
 	bne _080AE3BA
 	b _080AE678
 _080AE3BA:
-	movs r0, 0x80
+	movs r0, SOUND_CHANNEL_SF_START
 	tst r0, r6
 	beq _080AE3EA
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	tst r0, r6
 	bne _080AE3FA
-	movs r6, 0x3
-	strb r6, [r4, o_SoundChannel_status]
+	movs r6, SOUND_CHANNEL_SF_ENV_ATTACK
+	strb r6, [r4, o_SoundChannel_statusFlags]
 	adds r0, r3, 0
-	adds r0, 0x10
-	str r0, [r4, o_SoundChannel_cp]
-	ldr r0, [r3, 0xC]
-	str r0, [r4, o_SoundChannel_ct]
+	adds r0, o_WaveData_data
+	str r0, [r4, o_SoundChannel_currentPointer]
+	ldr r0, [r3, o_WaveData_size]
+	str r0, [r4, o_SoundChannel_count]
 	movs r5, 0
-	strb r5, [r4, o_SoundChannel_ev]
+	strb r5, [r4, o_SoundChannel_envelopeVolume]
 	str r5, [r4, o_SoundChannel_fw]
-	ldrb r2, [r3, 0x3]
-	movs r0, 0xC0
+	ldrb r2, [r3, o_WaveData_flags]
+	movs r0, WAVE_DATA_FLAG_LOOP
 	tst r0, r2
 	beq _080AE442
-	movs r0, 0x10
+	movs r0, SOUND_CHANNEL_SF_LOOP
 	orrs r6, r0
-	strb r6, [r4, o_SoundChannel_status]
+	strb r6, [r4, o_SoundChannel_statusFlags]
 	b _080AE442
 _080AE3EA:
-	ldrb r5, [r4, o_SoundChannel_ev]
-	movs r0, 0x4
+	ldrb r5, [r4, o_SoundChannel_envelopeVolume]
+	movs r0, SOUND_CHANNEL_SF_IEC
 	tst r0, r6
 	beq _080AE400
-	ldrb r0, [r4, o_SoundChannel_iel]
-	subs r0, 0x1
-	strb r0, [r4, o_SoundChannel_iel]
+	ldrb r0, [r4, o_SoundChannel_pseudoEchoLength]
+	subs r0, 1
+	strb r0, [r4, o_SoundChannel_pseudoEchoLength]
 	bhi _080AE450
 _080AE3FA:
 	movs r0, 0
-	strb r0, [r4, o_SoundChannel_status]
+	strb r0, [r4, o_SoundChannel_statusFlags]
 	b _080AE678
 _080AE400:
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	tst r0, r6
 	beq _080AE420
 	ldrb r0, [r4, o_SoundChannel_release]
 	muls r5, r0
 	lsrs r5, 8
-	ldrb r0, [r4, o_SoundChannel_iev]
+	ldrb r0, [r4, o_SoundChannel_pseudoEchoVolume]
 	cmp r5, r0
 	bhi _080AE450
 _080AE412:
-	ldrb r5, [r4, o_SoundChannel_iev]
+	ldrb r5, [r4, o_SoundChannel_pseudoEchoVolume]
 	cmp r5, 0
 	beq _080AE3FA
-	movs r0, 0x4
+	movs r0, SOUND_CHANNEL_SF_IEC
 	orrs r6, r0
-	strb r6, [r4, o_SoundChannel_status]
+	strb r6, [r4, o_SoundChannel_statusFlags]
 	b _080AE450
 _080AE420:
-	movs r2, 0x3
+	movs r2, SOUND_CHANNEL_SF_ENV
 	ands r2, r6
-	cmp r2, 0x2
+	cmp r2, SOUND_CHANNEL_SF_ENV_DECAY
 	bne _080AE43E
 	ldrb r0, [r4, o_SoundChannel_decay]
 	muls r5, r0
@@ -243,10 +243,10 @@ _080AE420:
 	adds r5, r0, 0
 	beq _080AE412
 	subs r6, 0x1
-	strb r6, [r4, o_SoundChannel_status]
+	strb r6, [r4, o_SoundChannel_statusFlags]
 	b _080AE450
 _080AE43E:
-	cmp r2, 0x3
+	cmp r2, SOUND_CHANNEL_SF_ENV_ATTACK
 	bne _080AE450
 _080AE442:
 	ldrb r0, [r4, o_SoundChannel_attack]
@@ -255,9 +255,9 @@ _080AE442:
 	bcc _080AE450
 	movs r5, 0xFF
 	subs r6, 0x1
-	strb r6, [r4, o_SoundChannel_status]
+	strb r6, [r4, o_SoundChannel_statusFlags]
 _080AE450:
-	strb r5, [r4, o_SoundChannel_ev]
+	strb r5, [r4, o_SoundChannel_envelopeVolume]
 	ldr r0, [sp, 0x18]
 	ldrb r0, [r0, o_SoundChannel_release]
 	adds r0, 0x1
@@ -266,34 +266,34 @@ _080AE450:
 	ldrb r0, [r4, o_SoundChannel_rightVolume]
 	muls r0, r5
 	lsrs r0, 8
-	strb r0, [r4, o_SoundChannel_er]
+	strb r0, [r4, o_SoundChannel_envelopeVolumeRight]
 	ldrb r0, [r4, o_SoundChannel_leftVolume]
 	muls r0, r5
 	lsrs r0, 8
-	strb r0, [r4, o_SoundChannel_el]
-	movs r0, 0x10
+	strb r0, [r4, o_SoundChannel_envelopeVolumeLeft]
+	movs r0, SOUND_CHANNEL_SF_LOOP
 	ands r0, r6
 	str r0, [sp, 0x10]
 	beq _080AE484
 	adds r0, r3, 0
-	adds r0, 0x10
-	ldr r1, [r3, 0x8]
+	adds r0, o_WaveData_data
+	ldr r1, [r3, o_WaveData_loopStart]
 	adds r0, r1
 	str r0, [sp, 0xC]
-	ldr r0, [r3, 0xC]
+	ldr r0, [r3, o_WaveData_size]
 	subs r0, r1
 	str r0, [sp, 0x10]
 _080AE484:
 	ldr r5, [sp, 0x8]
-	ldr r2, [r4, o_SoundChannel_ct]
-	ldr r3, [r4, o_SoundChannel_cp]
+	ldr r2, [r4, o_SoundChannel_count]
+	ldr r3, [r4, o_SoundChannel_currentPointer]
 	adr r0, _080AE490
 	bx r0
 	.arm
 _080AE490:
 	str r8, [sp]
-	ldrb r10, [r4, o_SoundChannel_er]
-	ldrb r11, [r4, o_SoundChannel_el]
+	ldrb r10, [r4, o_SoundChannel_envelopeVolumeRight]
+	ldrb r11, [r4, o_SoundChannel_envelopeVolumeLeft]
 	mov r10, r10, lsl 16
 	mov r11, r11, lsl 16
 	ldrb r0, [r4, o_SoundChannel_type]
@@ -313,7 +313,7 @@ _080AE4B0:
 	moveq r2, 0x4
 _080AE4DC:
 	ldr r6, [r5]
-	ldr r7, [r5, 0x630]
+	ldr r7, [r5, PCM_DMA_BUF_SIZE]
 _080AE4E4:
 	ldrsb r0, [r3], 0x1
 	mul r1, r10, r0
@@ -324,7 +324,7 @@ _080AE4E4:
 	add r7, r1, r7, ror 8
 	adds r5, r5, 0x40000000
 	bcc _080AE4E4
-	str r7, [r5, 0x630]
+	str r7, [r5, PCM_DMA_BUF_SIZE]
 	str r6, [r5], 0x4
 	subs r8, r8, 0x4
 	bgt _080AE4DC
@@ -332,7 +332,7 @@ _080AE4E4:
 	beq _080AE664
 _080AE520:
 	ldr r6, [r5]
-	ldr r7, [r5, 0x630]
+	ldr r7, [r5, PCM_DMA_BUF_SIZE]
 _080AE528:
 	ldrsb r0, [r3], 0x1
 	mul r1, r10, r0
@@ -346,7 +346,7 @@ _080AE528:
 _080AE54C:
 	adds r5, r5, 0x40000000
 	bcc _080AE528
-	str r7, [r5, 0x630]
+	str r7, [r5, PCM_DMA_BUF_SIZE]
 	str r6, [r5], 0x4
 	subs r8, r8, 0x4
 	bgt _080AE4B0
@@ -372,27 +372,27 @@ _080AE598:
 	ldrne r3, [sp, 0xC]
 	bne _080AE54C
 _080AE5A8:
-	strb r2, [r4, o_SoundChannel_status]
+	strb r2, [r4, o_SoundChannel_statusFlags]
 	mov r0, r5, lsr 30
 	bic r5, r5, 0xC0000000
 	rsb r0, r0, 0x3
 	mov r0, r0, lsl 3
 	mov r6, r6, ror r0
 	mov r7, r7, ror r0
-	str r7, [r5, 0x630]
+	str r7, [r5, PCM_DMA_BUF_SIZE]
 	str r6, [r5], 0x4
 	b _080AE66C
 _080AE5D0:
 	stmdb sp!, {r4,r12}
 	ldr lr, [r4, o_SoundChannel_fw]
-	ldr r1, [r4, o_SoundChannel_freq]
+	ldr r1, [r4, o_SoundChannel_frequency]
 	mul r4, r12, r1
 	ldrsb r0, [r3]
 	ldrsb r1, [r3, 0x1]!
 	sub r1, r1, r0
 _080AE5EC:
 	ldr r6, [r5]
-	ldr r7, [r5, 0x630]
+	ldr r7, [r5, PCM_DMA_BUF_SIZE]
 _080AE5F4:
 	mul r9, lr, r1
 	add r9, r0, r9, asr 23
@@ -417,7 +417,7 @@ _080AE634:
 _080AE640:
 	adds r5, r5, 0x40000000
 	bcc _080AE5F4
-	str r7, [r5, 0x630]
+	str r7, [r5, PCM_DMA_BUF_SIZE]
 	str r6, [r5], 0x4
 	subs r8, r8, 0x4
 	bgt _080AE5EC
@@ -425,8 +425,8 @@ _080AE640:
 	ldmia sp!, {r4,r12}
 	str lr, [r4, o_SoundChannel_fw]
 _080AE664:
-	str r2, [r4, o_SoundChannel_ct]
-	str r3, [r4, o_SoundChannel_cp]
+	str r2, [r4, o_SoundChannel_count]
+	str r3, [r4, o_SoundChannel_currentPointer]
 _080AE66C:
 	ldr r8, [sp]
 	add r0, pc, 0x1
@@ -434,7 +434,7 @@ _080AE66C:
 	.thumb
 _080AE678:
 	ldr r0, [sp, 0x4]
-	subs r0, 0x1
+	subs r0, 1
 	ble _080AE682
 	adds r4, SoundChannel_size
 	b SoundMainRAM_ChanLoop
@@ -450,7 +450,7 @@ _080AE682:
 	mov r11, r3
 	pop {r3}
 
-call_r3:
+call_r3_:
 	bx r3
 	.pool
 	thumb_func_end SoundMainRAM
@@ -472,24 +472,24 @@ SoundMainBTM:
 
 	thumb_func_start RealClearChain
 RealClearChain:
-	ldr r3, [r0, 0x2C]
+	ldr r3, [r0, o_SoundChannel_track]
 	cmp r3, 0
 	beq _080AE6D2
-	ldr r1, [r0, 0x34]
-	ldr r2, [r0, 0x30]
+	ldr r1, [r0, o_SoundChannel_nextChannelPointer]
+	ldr r2, [r0, o_SoundChannel_prevChannelPointer]
 	cmp r2, 0
 	beq _080AE6C6
-	str r1, [r2, 0x34]
+	str r1, [r2, o_SoundChannel_nextChannelPointer]
 	b _080AE6C8
 _080AE6C6:
-	str r1, [r3, 0x20]
+	str r1, [r3, o_MusicPlayerTrack_chan]
 _080AE6C8:
 	cmp r1, 0
 	beq _080AE6CE
-	str r2, [r1, 0x30]
+	str r2, [r1, o_SoundChannel_prevChannelPointer]
 _080AE6CE:
 	movs r1, 0
-	str r1, [r0, 0x2C]
+	str r1, [r0, o_SoundChannel_track]
 _080AE6D2:
 	bx lr
 	thumb_func_end RealClearChain
@@ -502,22 +502,22 @@ ply_fine:
 	cmp r4, 0
 	beq ply_fine_done
 ply_fine_loop:
-	ldrb r1, [r4]
-	movs r0, 0xC7
+	ldrb r1, [r4, o_SoundChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r1
 	beq ply_fine_ok
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	orrs r1, r0
-	strb r1, [r4]
+	strb r1, [r4, o_SoundChannel_statusFlags]
 ply_fine_ok:
 	adds r0, r4, 0
 	bl RealClearChain
-	ldr r4, [r4, 0x34]
+	ldr r4, [r4, o_SoundChannel_nextChannelPointer]
 	cmp r4, 0
 	bne ply_fine_loop
 ply_fine_done:
 	movs r0, 0
-	strb r0, [r5]
+	strb r0, [r5, o_MusicPlayerTrack_flags]
 	pop {r4,r5}
 	pop {r0}
 	bx r0
@@ -543,30 +543,34 @@ MPlayJumpTableCopy_Loop:
 ldrb_r3_r2:
 	ldrb r3, [r2]
 
+@ This attempts to protect against reading anything from the BIOS ROM
+@ besides the jump table template.
+@ It assumes that the jump table template is located at the end of the ROM.
 	.thumb_func
 chk_adr_r2:
 	push {r0}
 	lsrs r0, r2, 25
-	bne chk_adr_r2_done 
+	bne chk_adr_r2_done @ if adr >= 0x2000000 (i.e. not in BIOS ROM), accept it
 	ldr r0, lt_MPlayJumpTableTemplate
 	cmp r2, r0
-	bcc chk_adr_r2_reject
+	blo chk_adr_r2_reject @ if adr < gMPlayJumpTableTemplate, reject it
 	lsrs r0, r2, 14
-	beq chk_adr_r2_done 
+	beq chk_adr_r2_done @ if adr < 0x40000 (i.e. in BIOS ROM), accept it
 chk_adr_r2_reject:
 	movs r3, 0
 chk_adr_r2_done:
 	pop {r0}
 	bx lr
+
 	.align 2, 0
 lt_MPlayJumpTableTemplate: .word gMPlayJumpTableTemplate
 
 	thumb_func_start ld_r3_tp_adr_i
 ld_r3_tp_adr_i:
-	ldr r2, [r1, 0x40]
+	ldr r2, [r1, o_MusicPlayerTrack_cmdPtr]
 _080AE73A:
 	adds r3, r2, 0x1
-	str r3, [r1, 0x40]
+	str r3, [r1, o_MusicPlayerTrack_cmdPtr]
 	ldrb r3, [r2]
 	b chk_adr_r2
 	thumb_func_end ld_r3_tp_adr_i
@@ -594,18 +598,18 @@ ply_goto_1:
 	thumb_func_start ply_patt
 ply_patt:
 	ldrb r2, [r1, o_MusicPlayerTrack_patternLevel]
-	cmp r2, 0x3
-	bcs _080AE77C
+	cmp r2, 3
+	bhs ply_patt_done
 	lsls r2, 2
 	adds r3, r1, r2
 	ldr r2, [r1, o_MusicPlayerTrack_cmdPtr]
 	adds r2, 0x4
 	str r2, [r3, o_MusicPlayerTrack_patternStack]
 	ldrb r2, [r1, o_MusicPlayerTrack_patternLevel]
-	adds r2, 0x1
+	adds r2, 1
 	strb r2, [r1, o_MusicPlayerTrack_patternLevel]
 	b ply_goto
-_080AE77C:
+ply_patt_done:
 	b ply_fine
 	thumb_func_end ply_patt
 
@@ -697,13 +701,13 @@ ply_voice:
 	lsls r2, 2
 	ldr r3, [r0, o_MusicPlayerInfo_tone]
 	adds r2, r3
-	ldr r3, [r2]
+	ldr r3, [r2, o_ToneData_type]
 	bl chk_adr_r2
 	str r3, [r1, o_MusicPlayerTrack_ToneData_type]
-	ldr r3, [r2, 0x4]
+	ldr r3, [r2, o_ToneData_wav]
 	bl chk_adr_r2
 	str r3, [r1, o_MusicPlayerTrack_ToneData_wav]
-	ldr r3, [r2, 0x8]
+	ldr r3, [r2, o_ToneData_attack]
 	bl chk_adr_r2
 	str r3, [r1, o_MusicPlayerTrack_ToneData_attack]
 	bx r12
@@ -715,7 +719,7 @@ ply_vol:
 	bl ld_r3_tp_adr_i
 	strb r3, [r1, o_MusicPlayerTrack_vol]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0x3
+	movs r2, MPT_FLG_VOLCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 	bx r12
@@ -725,10 +729,10 @@ ply_vol:
 ply_pan:
 	mov r12, lr
 	bl ld_r3_tp_adr_i
-	subs r3, 0x40
+	subs r3, C_V
 	strb r3, [r1, o_MusicPlayerTrack_pan]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0x3
+	movs r2, MPT_FLG_VOLCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 	bx r12
@@ -738,10 +742,10 @@ ply_pan:
 ply_bend:
 	mov r12, lr
 	bl ld_r3_tp_adr_i
-	subs r3, 0x40
+	subs r3, C_V
 	strb r3, [r1, o_MusicPlayerTrack_bend]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0xC
+	movs r2, MPT_FLG_PITCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 	bx r12
@@ -753,7 +757,7 @@ ply_bendr:
 	bl ld_r3_tp_adr_i
 	strb r3, [r1, o_MusicPlayerTrack_bendRange]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0xC
+	movs r2, MPT_FLG_PITCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 	bx r12
@@ -776,7 +780,7 @@ ply_modt:
 	beq _080AE89A
 	strb r3, [r1, o_MusicPlayerTrack_modT]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0xF
+	movs r2, MPT_FLG_VOLCHG | MPT_FLG_PITCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 _080AE89A:
@@ -787,10 +791,10 @@ _080AE89A:
 ply_tune:
 	mov r12, lr
 	bl ld_r3_tp_adr_i
-	subs r3, 0x40
+	subs r3, C_V
 	strb r3, [r1, o_MusicPlayerTrack_tune]
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
-	movs r2, 0xC
+	movs r2, MPT_FLG_PITCHG
 	orrs r3, r2
 	strb r3, [r1, o_MusicPlayerTrack_flags]
 	bx r12
@@ -801,7 +805,7 @@ ply_port:
 	mov r12, lr
 	ldr r2, [r1, o_MusicPlayerTrack_cmdPtr]
 	ldrb r3, [r2]
-	adds r2, 0x1
+	adds r2, 1
 	ldr r0, =REG_SOUND1CNT_L @ sound register base address
 	adds r0, r3
 	bl _080AE73A
@@ -819,15 +823,15 @@ m4aSoundVSync:
 	ldr r2, lt2_ID_NUMBER
 	ldr r3, [r0, o_SoundInfo_ident]
 	subs r3, r2
-	cmp r3, 0x1
+	cmp r3, 1
 	bhi m4aSoundVSync_Done
 
 	@ Decrement the PCM DMA counter. If it reaches 0, we need to do a DMA.
 	ldrb r1, [r0, o_SoundInfo_pcmDmaCounter]
-	subs r1, 0x1
+	subs r1, 1
 	strb r1, [r0, o_SoundInfo_pcmDmaCounter]
 	bgt m4aSoundVSync_Done
-	
+
 	@ Reload the PCM DMA counter.
 	ldrb r1, [r0, o_SoundInfo_pcmDmaPeriod]
 	strb r1, [r0, o_SoundInfo_pcmDmaCounter]
@@ -836,7 +840,7 @@ m4aSoundVSync:
 
 	ldr r1, [r2, 0x8] @ DMA1CNT
 	lsls r1, 7
-	bcc m4aSoundVSync_SkipDMA1 
+	bcc m4aSoundVSync_SkipDMA1 @ branch if repeat bit isn't set
 
 	ldr r1, =((DMA_ENABLE | DMA_START_NOW | DMA_32BIT | DMA_SRC_INC | DMA_DEST_FIXED) << 16) | 4
 	str r1, [r2, 0x8] @ DMA1CNT
@@ -844,16 +848,20 @@ m4aSoundVSync:
 m4aSoundVSync_SkipDMA1:
 	ldr r1, [r2, 0xC + 0x8] @ DMA2CNT
 	lsls r1, 7
-	bcc m4aSoundVSync_SkipDMA2
+	bcc m4aSoundVSync_SkipDMA2 @ branch if repeat bit isn't set
+
 	ldr r1, =((DMA_ENABLE | DMA_START_NOW | DMA_32BIT | DMA_SRC_INC | DMA_DEST_FIXED) << 16) | 4
 	str r1, [r2, 0xC + 0x8] @ DMA2CNT
 
 m4aSoundVSync_SkipDMA2:
+
+	@ turn off DMA1/DMA2
 	movs r1, DMA_32BIT >> 8
 	lsls r1, 8
 	strh r1, [r2, 0xA]       @ DMA1CNT_H
 	strh r1, [r2, 0xC + 0xA] @ DMA2CNT_H
 
+	@ turn on DMA1/DMA2 direct-sound FIFO mode
 	movs r1, (DMA_ENABLE | DMA_START_SPECIAL | DMA_32BIT | DMA_REPEAT) >> 8
 	lsls r1, 8 @ LSB is 0, so DMA_SRC_INC is used (destination is always fixed in FIFO mode)
 	strh r1, [r2, 0xA]       @ DMA1CNT_H
@@ -880,7 +888,7 @@ _080AE91E:
 	cmp r3, 0
 	beq _080AE930
 	ldr r0, [r0, o_MusicPlayerInfo_intp]
-	bl call_r3_2
+	bl call_r3
 _080AE930:
 	pop {r0}
 	push {r4-r7}
@@ -915,8 +923,8 @@ _080AE964:
 	movs r3, 0x1
 	movs r4, 0
 _080AE96C:
-	ldrb r0, [r5]
-	movs r1, 0x80
+	ldrb r0, [r5, o_MusicPlayerTrack_flags]
+	movs r1, MPT_FLG_EXIST
 	tst r1, r0
 	bne _080AE976
 	b _080AEA88
@@ -928,36 +936,36 @@ _080AE976:
 	cmp r4, 0
 	beq _080AE9AA
 _080AE982:
-	ldrb r1, [r4]
-	movs r0, 0xC7
+	ldrb r1, [r4, o_SoundChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r1
 	beq _080AE99E
-	ldrb r0, [r4, 0x10]
+	ldrb r0, [r4, o_SoundChannel_gateTime]
 	cmp r0, 0
 	beq _080AE9A4
 	subs r0, 0x1
-	strb r0, [r4, 0x10]
+	strb r0, [r4, o_SoundChannel_gateTime]
 	bne _080AE9A4
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	orrs r1, r0
-	strb r1, [r4]
+	strb r1, [r4, o_SoundChannel_statusFlags]
 	b _080AE9A4
 _080AE99E:
 	adds r0, r4, 0
 	bl ClearChain
 _080AE9A4:
-	ldr r4, [r4, 0x34]
+	ldr r4, [r4, o_SoundChannel_nextChannelPointer]
 	cmp r4, 0
 	bne _080AE982
 _080AE9AA:
 	ldrb r3, [r5, o_MusicPlayerTrack_flags]
-	movs r0, 0x40
+	movs r0, MPT_FLG_START
 	tst r0, r3
 	beq _080AEA28
 	adds r0, r5, 0
 	bl Clear64byte
-	movs r0, 0x80
-	strb r0, [r5]
+	movs r0, MPT_FLG_EXIST
+	strb r0, [r5, o_MusicPlayerTrack_flags]
 	movs r0, 0x2
 	strb r0, [r5, o_MusicPlayerTrack_bendRange]
 	movs r0, 0x40
@@ -990,7 +998,7 @@ _080AE9E6:
 	subs r0, 0xCF
 	adds r1, r7, 0
 	adds r2, r5, 0
-	bl call_r3_2
+	bl call_r3
 	b _080AEA28
 _080AE9FC:
 	cmp r1, 0xB0
@@ -1004,7 +1012,7 @@ _080AE9FC:
 	ldr r3, [r3, r0]
 	adds r0, r7, 0
 	adds r1, r5, 0
-	bl call_r3_2
+	bl call_r3
 	ldrb r0, [r5, o_MusicPlayerTrack_flags]
 	cmp r0, 0
 	beq _080AEA84
@@ -1060,10 +1068,10 @@ _080AEA62:
 	ldrb r1, [r5, o_MusicPlayerTrack_modT]
 	cmp r1, 0
 	bne _080AEA7E
-	movs r1, 0xC
+	movs r1, MPT_FLG_PITCHG
 	b _080AEA80
 _080AEA7E:
-	movs r1, 0x3
+	movs r1, MPT_FLG_VOLCHG
 _080AEA80:
 	orrs r0, r1
 	strb r0, [r5, o_MusicPlayerTrack_flags]
@@ -1073,7 +1081,7 @@ _080AEA84:
 _080AEA88:
 	subs r6, 0x1
 	ble _080AEA94
-	movs r0, 0x50
+	movs r0, MusicPlayerTrack_size
 	adds r5, r0
 	lsls r3, 1
 	b _080AE96C
@@ -1090,10 +1098,10 @@ _080AEA94:
 _080AEAA6:
 	str r4, [r7, o_MusicPlayerInfo_status]
 	ldrh r0, [r7, o_MusicPlayerInfo_tempoC]
-	subs r0, 0x96
+	subs r0, 150
 _080AEAAC:
 	strh r0, [r7, o_MusicPlayerInfo_tempoC]
-	cmp r0, 0x96
+	cmp r0, 150
 	bcc _080AEAB4
 	b _080AE964
 _080AEAB4:
@@ -1104,7 +1112,7 @@ _080AEAB8:
 	movs r1, 0x80
 	tst r1, r0
 	beq _080AEB52
-	movs r1, 0xF
+	movs r1, MPT_FLG_VOLCHG | MPT_FLG_PITCHG
 	tst r1, r0
 	beq _080AEB52
 	mov r9, r2
@@ -1115,8 +1123,8 @@ _080AEAB8:
 	cmp r4, 0
 	beq _080AEB48
 _080AEAD6:
-	ldrb r1, [r4, o_SoundChannel_status]
-	movs r0, 0xC7
+	ldrb r1, [r4, o_SoundChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r1
 	bne _080AEAE6
 	adds r0, r4, 0
@@ -1124,26 +1132,26 @@ _080AEAD6:
 	b _080AEB42
 _080AEAE6:
 	ldrb r0, [r4, o_SoundChannel_type]
-	movs r6, 0x7
+	movs r6, TONEDATA_TYPE_CGB
 	ands r6, r0
 	ldrb r3, [r5, o_MusicPlayerTrack_flags]
-	movs r0, 0x3
+	movs r0, MPT_FLG_VOLCHG
 	tst r0, r3
 	beq _080AEB04
 	bl ChnVolSetAsm
 	cmp r6, 0
 	beq _080AEB04
-	ldrb r0, [r4, o_CgbChannel_mo]
-	movs r1, 0x1
+	ldrb r0, [r4, o_CgbChannel_modify]
+	movs r1, CGB_CHANNEL_MO_VOL
 	orrs r0, r1
-	strb r0, [r4, o_CgbChannel_mo]
+	strb r0, [r4, o_CgbChannel_modify]
 _080AEB04:
 	ldrb r3, [r5, o_MusicPlayerTrack_flags]
-	movs r0, 0xC
+	movs r0, MPT_FLG_PITCHG
 	tst r0, r3
 	beq _080AEB42
-	ldrb r1, [r4, o_SoundChannel_ky]
-	movs r0, 0x8
+	ldrb r1, [r4, o_SoundChannel_key]
+	movs r0, o_MusicPlayerTrack_keyM
 	ldrsb r0, [r5, r0]
 	adds r2, r1, r0
 	bpl _080AEB18
@@ -1156,21 +1164,21 @@ _080AEB18:
 	adds r1, r2, 0
 	ldrb r2, [r5, o_MusicPlayerTrack_pitM]
 	adds r0, r6, 0
-	bl call_r3_2
-	str r0, [r4, o_CgbChannel_fr]
-	ldrb r0, [r4, o_CgbChannel_mo]
-	movs r1, 0x2
+	bl call_r3
+	str r0, [r4, o_CgbChannel_frequency]
+	ldrb r0, [r4, o_CgbChannel_modify]
+	movs r1, CGB_CHANNEL_MO_PIT
 	orrs r0, r1
-	strb r0, [r4, o_CgbChannel_mo]
+	strb r0, [r4, o_CgbChannel_modify]
 	b _080AEB42
 _080AEB36:
 	adds r1, r2, 0
 	ldrb r2, [r5, o_MusicPlayerTrack_pitM]
 	ldr r0, [r4, o_SoundChannel_wav]
 	bl MidiKeyToFreq
-	str r0, [r4, o_SoundChannel_freq]
+	str r0, [r4, o_SoundChannel_frequency]
 _080AEB42:
-	ldr r4, [r4, o_SoundChannel_np]
+	ldr r4, [r4, o_SoundChannel_nextChannelPointer]
 	cmp r4, 0
 	bne _080AEAD6
 _080AEB48:
@@ -1182,7 +1190,7 @@ _080AEB48:
 _080AEB52:
 	subs r2, 0x1
 	ble _080AEB5C
-	movs r0, 0x50
+	movs r0, MusicPlayerTrack_size
 	adds r5, r0
 	bgt _080AEAB8
 _080AEB5C:
@@ -1194,10 +1202,11 @@ _080AEB5C:
 	mov r10, r2
 	mov r11, r3
 	pop {r3}
-call_r3_2:
+
+call_r3:
 	bx r3
-	.align 2, 0
 
+	.align 2, 0
 lt_gClockTable:     .word gClockTable
 lt2_SOUND_INFO_PTR: .word SOUND_INFO_PTR
 lt2_ID_NUMBER:      .word ID_NUMBER
@@ -1208,7 +1217,7 @@ TrackStop:
 	push {r4-r6,lr}
 	adds r5, r1, 0
 	ldrb r1, [r5, o_MusicPlayerTrack_flags]
-	movs r0, 0x80
+	movs r0, MPT_FLG_EXIST
 	tst r0, r1
 	beq TrackStop_Done
 	ldr r4, [r5, o_MusicPlayerTrack_chan]
@@ -1216,22 +1225,22 @@ TrackStop:
 	beq TrackStop_3
 	movs r6, 0
 TrackStop_Loop:
-	ldrb r0, [r4, o_SoundChannel_status]
+	ldrb r0, [r4, o_SoundChannel_statusFlags]
 	cmp r0, 0
 	beq TrackStop_2
 	ldrb r0, [r4, o_SoundChannel_type]
-	movs r3, 0x7
+	movs r3, TONEDATA_TYPE_CGB
 	ands r0, r3
 	beq TrackStop_1
 	ldr r3, =SOUND_INFO_PTR
 	ldr r3, [r3]
 	ldr r3, [r3, o_SoundInfo_CgbOscOff]
-	bl call_r3_2
+	bl call_r3
 TrackStop_1:
-	strb r6, [r4, o_SoundChannel_status]
+	strb r6, [r4, o_SoundChannel_statusFlags]
 TrackStop_2:
 	str r6, [r4, o_SoundChannel_track]
-	ldr r4, [r4, o_SoundChannel_np]
+	ldr r4, [r4, o_SoundChannel_nextChannelPointer]
 	cmp r4, 0
 	bne TrackStop_Loop
 TrackStop_3:
@@ -1245,31 +1254,31 @@ TrackStop_Done:
 
 	thumb_func_start ChnVolSetAsm
 ChnVolSetAsm:
-	ldrb r1, [r4, 0x12]
-	movs r0, 0x14
+	ldrb r1, [r4, o_SoundChannel_velocity]
+	movs r0, o_SoundChannel_rhythmPan
 	ldrsb r2, [r4, r0]
 	movs r3, 0x80
 	adds r3, r2
 	muls r3, r1
-	ldrb r0, [r5, 0x10]
+	ldrb r0, [r5, o_MusicPlayerTrack_volMR]
 	muls r0, r3
 	asrs r0, 14
 	cmp r0, 0xFF
 	bls _080AEBD8
 	movs r0, 0xFF
 _080AEBD8:
-	strb r0, [r4, 0x2]
+	strb r0, [r4, o_SoundChannel_rightVolume]
 	movs r3, 0x7F
 	subs r3, r2
 	muls r3, r1
-	ldrb r0, [r5, 0x11]
+	ldrb r0, [r5, o_MusicPlayerTrack_volML]
 	muls r0, r3
 	asrs r0, 14
 	cmp r0, 0xFF
 	bls _080AEBEC
 	movs r0, 0xFF
 _080AEBEC:
-	strb r0, [r4, 0x3]
+	strb r0, [r4, o_SoundChannel_leftVolume]
 	bx lr
 	thumb_func_end ChnVolSetAsm
 
@@ -1294,17 +1303,17 @@ ply_note:
 	ldr r3, [r5, o_MusicPlayerTrack_cmdPtr]
 	ldrb r0, [r3]
 	cmp r0, 0x80
-	bcs _080AEC36
+	bhs _080AEC36
 	strb r0, [r5, o_MusicPlayerTrack_key]
 	adds r3, 0x1
 	ldrb r0, [r3]
 	cmp r0, 0x80
-	bcs _080AEC34
+	bhs _080AEC34
 	strb r0, [r5, o_MusicPlayerTrack_velocity]
 	adds r3, 0x1
 	ldrb r0, [r3]
 	cmp r0, 0x80
-	bcs _080AEC34
+	bhs _080AEC34
 	ldrb r1, [r5, o_MusicPlayerTrack_gateTime]
 	adds r1, r0
 	strb r1, [r5, o_MusicPlayerTrack_gateTime]
@@ -1339,32 +1348,32 @@ _080AEC58:
 	mov r9, r1
 	mov r6, r9
 	ldrb r1, [r6]
-	movs r0, 0xC0
+	movs r0, TONEDATA_TYPE_SPL | TONEDATA_TYPE_RHY
 	tst r0, r1
 	beq _080AEC70
 	b _080AEDD6
 _080AEC70:
-	movs r0, 0x80
+	movs r0, TONEDATA_TYPE_RHY
 	tst r0, r2
 	beq _080AEC8C
-	ldrb r1, [r6, 0x3]
+	ldrb r1, [r6, o_ToneData_pan_sweep]
 	movs r0, 0x80
 	tst r0, r1
 	beq _080AEC84
-	subs r1, 0xC0
+	subs r1, TONEDATA_P_S_PAN
 	lsls r1, 1
 	str r1, [sp, 0x14]
 _080AEC84:
-	ldrb r3, [r6, 0x1]
+	ldrb r3, [r6, o_SoundChannel_type]
 	b _080AEC8C
 _080AEC88:
 	mov r9, r4
-	ldrb r3, [r5, 0x5]
+	ldrb r3, [r5, o_MusicPlayerTrack_key]
 _080AEC8C:
 	str r3, [sp, 0x8]
 	ldr r6, [sp]
-	ldrb r1, [r6, 0x9]
-	ldrb r0, [r5, 0x1D]
+	ldrb r1, [r6, o_MusicPlayerInfo_priority]
+	ldrb r0, [r5, o_MusicPlayerTrack_priority]
 	adds r0, r1
 	cmp r0, 0xFF
 	bls _080AEC9C
@@ -1372,13 +1381,13 @@ _080AEC8C:
 _080AEC9C:
 	str r0, [sp, 0x10]
 	mov r6, r9
-	ldrb r0, [r6]
-	movs r6, 0x7
+	ldrb r0, [r6, o_ToneData_type]
+	movs r6, TONEDATA_TYPE_CGB
 	ands r6, r0
 	str r6, [sp, 0xC]
 	beq _080AECDC
 	ldr r0, [sp, 0x4]
-	ldr r4, [r0, 0x1C]
+	ldr r4, [r0, o_SoundInfo_cgbChans]
 	cmp r4, 0
 	bne _080AECB4
 	b _080AEDD6
@@ -1386,21 +1395,21 @@ _080AECB4:
 	subs r6, 0x1
 	lsls r0, r6, 6
 	adds r4, r0
-	ldrb r1, [r4]
-	movs r0, 0xC7
+	ldrb r1, [r4, o_CgbChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r1
 	beq _080AED30
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	tst r0, r1
 	bne _080AED30
-	ldrb r1, [r4, 0x13]
+	ldrb r1, [r4, o_CgbChannel_priority]
 	ldr r0, [sp, 0x10]
 	cmp r1, r0
 	bcc _080AED30
 	beq _080AECD4
 	b _080AEDD6
 _080AECD4:
-	ldr r0, [r4, 0x2C]
+	ldr r0, [r4, o_CgbChannel_track]
 	cmp r0, r5
 	bcs _080AED30
 	b _080AEDD6
@@ -1410,35 +1419,35 @@ _080AECDC:
 	movs r2, 0
 	mov r8, r2
 	ldr r4, [sp, 0x4]
-	ldrb r3, [r4, 0x6]
-	adds r4, 0x50
+	ldrb r3, [r4, o_SoundInfo_maxChans]
+	adds r4, o_SoundInfo_chans
 _080AECEA:
-	ldrb r1, [r4]
-	movs r0, 0xC7
+	ldrb r1, [r4, o_SoundChannel_statusFlags]
+	movs r0, SOUND_CHANNEL_SF_ON
 	tst r0, r1
 	beq _080AED30
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	tst r0, r1
 	beq _080AED04
 	cmp r2, 0
 	bne _080AED08
 	adds r2, 0x1
-	ldrb r6, [r4, 0x13]
-	ldr r7, [r4, 0x2C]
+	ldrb r6, [r4, o_SoundChannel_priority]
+	ldr r7, [r4, o_SoundChannel_track]
 	b _080AED22
 _080AED04:
 	cmp r2, 0
 	bne _080AED24
 _080AED08:
-	ldrb r0, [r4, 0x13]
+	ldrb r0, [r4, o_SoundChannel_priority]
 	cmp r0, r6
 	bcs _080AED14
 	adds r6, r0, 0
-	ldr r7, [r4, 0x2C]
+	ldr r7, [r4, o_SoundChannel_track]
 	b _080AED22
 _080AED14:
 	bhi _080AED24
-	ldr r0, [r4, 0x2C]
+	ldr r0, [r4, o_SoundChannel_track]
 	cmp r0, r7
 	bls _080AED20
 	adds r7, r0, 0
@@ -1448,7 +1457,7 @@ _080AED20:
 _080AED22:
 	mov r8, r4
 _080AED24:
-	adds r4, 0x40
+	adds r4, SoundChannel_size
 	subs r3, 0x1
 	bgt _080AECEA
 	mov r4, r8
@@ -1458,17 +1467,17 @@ _080AED30:
 	adds r0, r4, 0
 	bl ClearChain
 	movs r1, 0
-	str r1, [r4, 0x30]
-	ldr r3, [r5, 0x20]
-	str r3, [r4, 0x34]
+	str r1, [r4, o_SoundChannel_prevChannelPointer]
+	ldr r3, [r5, o_MusicPlayerTrack_chan]
+	str r3, [r4, o_SoundChannel_nextChannelPointer]
 	cmp r3, 0
 	beq _080AED44
-	str r4, [r3, 0x30]
+	str r4, [r3, o_SoundChannel_prevChannelPointer]
 _080AED44:
-	str r4, [r5, 0x20]
-	str r5, [r4, 0x2C]
-	ldrb r0, [r5, 0x1B]
-	strb r0, [r5, 0x1C]
+	str r4, [r5, o_MusicPlayerTrack_chan]
+	str r5, [r4, o_SoundChannel_track]
+	ldrb r0, [r5, o_MusicPlayerTrack_lfoDelay]
+	strb r0, [r5, o_MusicPlayerTrack_lfoDelayC]
 	cmp r0, r1
 	beq _080AED56
 	adds r1, r5, 0
@@ -1477,26 +1486,26 @@ _080AED56:
 	ldr r0, [sp]
 	adds r1, r5, 0
 	bl TrkVolPitSet
-	ldr r0, [r5, 0x4]
-	str r0, [r4, 0x10]
+	ldr r0, [r5, o_MusicPlayerTrack_gateTime]
+	str r0, [r4, o_SoundChannel_gateTime]
 	ldr r0, [sp, 0x10]
-	strb r0, [r4, 0x13]
+	strb r0, [r4, o_SoundChannel_priority]
 	ldr r0, [sp, 0x8]
-	strb r0, [r4, 0x8]
+	strb r0, [r4, o_SoundChannel_key]
 	ldr r0, [sp, 0x14]
-	strb r0, [r4, 0x14]
+	strb r0, [r4, o_SoundChannel_rhythmPan]
 	mov r6, r9
-	ldrb r0, [r6]
-	strb r0, [r4, 0x1]
-	ldr r7, [r6, 0x4]
-	str r7, [r4, 0x24]
-	ldr r0, [r6, 0x8]
-	str r0, [r4, 0x4]
-	ldrh r0, [r5, 0x1E]
-	strh r0, [r4, 0xC]
+	ldrb r0, [r6, o_ToneData_type]
+	strb r0, [r4, o_SoundChannel_type]
+	ldr r7, [r6, o_ToneData_wav]
+	str r7, [r4, o_SoundChannel_wav]
+	ldr r0, [r6, o_ToneData_attack]
+	str r0, [r4, o_SoundChannel_attack]
+	ldrh r0, [r5, o_MusicPlayerTrack_pseudoEchoVolume]
+	strh r0, [r4, o_SoundChannel_pseudoEchoVolume]
 	bl ChnVolSetAsm
-	ldrb r1, [r4, 0x8]
-	movs r0, 0x8
+	ldrb r1, [r4, o_SoundChannel_key]
+	movs r0, o_MusicPlayerTrack_keyM
 	ldrsb r0, [r5, r0]
 	adds r3, r1, r0
 	bpl _080AED90
@@ -1506,9 +1515,9 @@ _080AED90:
 	cmp r6, 0
 	beq _080AEDBE
 	mov r6, r9
-	ldrb r0, [r6, 0x2]
-	strb r0, [r4, 0x1E]
-	ldrb r1, [r6, 0x3]
+	ldrb r0, [r6, o_ToneData_length]
+	strb r0, [r4, o_CgbChannel_length]
+	ldrb r1, [r6, o_ToneData_pan_sweep]
 	movs r0, 0x80
 	tst r0, r1
 	bne _080AEDAA
@@ -1518,27 +1527,27 @@ _080AED90:
 _080AEDAA:
 	movs r1, 0x8
 _080AEDAC:
-	strb r1, [r4, 0x1F]
-	ldrb r2, [r5, 0x9]
+	strb r1, [r4, o_CgbChannel_sweep]
+	ldrb r2, [r5, o_MusicPlayerTrack_pitM]
 	adds r1, r3, 0
 	ldr r0, [sp, 0xC]
 	ldr r3, [sp, 0x4]
-	ldr r3, [r3, 0x30]
-	bl call_r3_2
+	ldr r3, [r3, o_SoundInfo_MidiKeyToCgbFreq]
+	bl call_r3
 	b _080AEDC8
 _080AEDBE:
-	ldrb r2, [r5, 0x9]
+	ldrb r2, [r5, o_MusicPlayerTrack_pitM]
 	adds r1, r3, 0
 	adds r0, r7, 0
 	bl MidiKeyToFreq
 _080AEDC8:
-	str r0, [r4, 0x20]
-	movs r0, 0x80
-	strb r0, [r4]
-	ldrb r1, [r5]
+	str r0, [r4, o_SoundChannel_frequency]
+	movs r0, SOUND_CHANNEL_SF_START
+	strb r0, [r4, o_SoundChannel_statusFlags]
+	ldrb r1, [r5, o_MusicPlayerTrack_flags]
 	movs r0, 0xF0
 	ands r0, r1
-	strb r0, [r5]
+	strb r0, [r5, o_MusicPlayerTrack_flags]
 _080AEDD6:
 	add sp, 0x18
 	pop {r0-r7}
@@ -1557,7 +1566,7 @@ ply_endtie:
 	ldr r2, [r1, o_MusicPlayerTrack_cmdPtr]
 	ldrb r3, [r2]
 	cmp r3, 0x80
-	bcs _080AEE02
+	bhs _080AEE02
 	strb r3, [r1, o_MusicPlayerTrack_key]
 	adds r2, 0x1
 	str r2, [r1, o_MusicPlayerTrack_cmdPtr]
@@ -1568,23 +1577,23 @@ _080AEE04:
 	ldr r1, [r1, o_MusicPlayerTrack_chan]
 	cmp r1, 0
 	beq _080AEE2C
-	movs r4, 0x83
-	movs r5, 0x40
+	movs r4, SOUND_CHANNEL_SF_START | SOUND_CHANNEL_SF_ENV
+	movs r5, SOUND_CHANNEL_SF_STOP
 _080AEE0E:
-	ldrb r2, [r1, o_SoundChannel_status]
+	ldrb r2, [r1, o_SoundChannel_statusFlags]
 	tst r2, r4
 	beq _080AEE26
 	tst r2, r5
 	bne _080AEE26
-	ldrb r0, [r1, o_SoundChannel_mk]
+	ldrb r0, [r1, o_SoundChannel_midiKey]
 	cmp r0, r3
 	bne _080AEE26
-	movs r0, 0x40
+	movs r0, SOUND_CHANNEL_SF_STOP
 	orrs r2, r0
-	strb r2, [r1, o_SoundChannel_status]
+	strb r2, [r1, o_SoundChannel_statusFlags]
 	b _080AEE2C
 _080AEE26:
-	ldr r1, [r1, o_SoundChannel_np]
+	ldr r1, [r1, o_SoundChannel_nextChannelPointer]
 	cmp r1, 0
 	bne _080AEE0E
 _080AEE2C:
@@ -1600,10 +1609,10 @@ clear_modM:
 	ldrb r2, [r1, o_MusicPlayerTrack_modT]
 	cmp r2, 0
 	bne _080AEE40
-	movs r2, 0xC
+	movs r2, MPT_FLG_PITCHG
 	b _080AEE42
 _080AEE40:
-	movs r2, 0x3
+	movs r2, MPT_FLG_VOLCHG
 _080AEE42:
 	ldrb r3, [r1, o_MusicPlayerTrack_flags]
 	orrs r3, r2
@@ -1613,9 +1622,9 @@ _080AEE42:
 
 	thumb_func_start ld_r3_tp_adr_i_unchecked
 ld_r3_tp_adr_i_unchecked:
-	ldr r2, [r1, 0x40]
-	adds r3, r2, 0x1
-	str r3, [r1, 0x40]
+	ldr r2, [r1, o_MusicPlayerTrack_cmdPtr]
+	adds r3, r2, 1
+	str r3, [r1, o_MusicPlayerTrack_cmdPtr]
 	ldrb r3, [r2]
 	bx lr
 	thumb_func_end ld_r3_tp_adr_i_unchecked