Incorporate the rest of the audio engine.

1 files changed, 2850 insertions, 0 deletions

diff --git a/audio/engine.asm b/audio/engine.asm
new file mode 100644
index 00000000..6b0fe1a6
--- /dev/null
+++ b/audio/engine.asm
@@ -0,0 +1,2850 @@
+; The entire sound engine. Uses section "audio" in WRAM.
+
+; Interfaces are in bank 0.
+
+; Notable functions:
+; 	FadeMusic
+; 	PlayStereoSFX
+
+_MapSetup_Sound_Off::
+; restart sound operation
+; clear all relevant hardware registers & wram
+	push hl
+	push de
+	push bc
+	push af
+	call MusicOff
+	ld hl, rNR50 ; channel control registers
+	xor a
+	ld [hli], a ; rNR50 ; volume/vin
+	ld [hli], a ; rNR51 ; sfx channels
+	ld a, $80 ; all channels on
+	ld [hli], a ; ff26 ; music channels
+
+	ld hl, rNR10 ; sound channel registers
+	ld e, NUM_MUSIC_CHANS
+.clearsound
+;   sound channel   1      2      3      4
+	xor a
+	ld [hli], a ; rNR10, rNR20, rNR30, rNR40 ; sweep = 0
+
+	ld [hli], a ; rNR11, rNR21, rNR31, rNR41 ; length/wavepattern = 0
+	ld a, $8
+	ld [hli], a ; rNR12, rNR22, rNR32, rNR42 ; envelope = 0
+	xor a
+	ld [hli], a ; rNR13, rNR23, rNR33, rNR43 ; frequency lo = 0
+	ld a, $80
+	ld [hli], a ; rNR14, rNR24, rNR34, rNR44 ; restart sound (freq hi = 0)
+	dec e
+	jr nz, .clearsound
+
+	ld hl, wChannels ; start of channel data
+	ld de, wChannelsEnd - wChannels ; length of area to clear (entire sound wram area)
+.clearchannels
+	xor a
+	ld [hli], a
+	dec de
+	ld a, e
+	or d
+	jr nz, .clearchannels
+	ld a, MAX_VOLUME
+	ld [wVolume], a
+	call MusicOn
+	pop af
+	pop bc
+	pop de
+	pop hl
+	ret
+
+MusicFadeRestart:
+; restart but keep the music id to fade in to
+	ld a, [wMusicFadeID + 1]
+	push af
+	ld a, [wMusicFadeID]
+	push af
+	call _MapSetup_Sound_Off
+	pop af
+	ld [wMusicFadeID], a
+	pop af
+	ld [wMusicFadeID + 1], a
+	ret
+
+MusicOn:
+	ld a, 1
+	ld [wMusicPlaying], a
+	ret
+
+MusicOff:
+	xor a
+	ld [wMusicPlaying], a
+	ret
+
+_UpdateSound::
+; called once per frame
+	; no use updating audio if it's not playing
+	ld a, [wMusicPlaying]
+	and a
+	ret z
+	; start at ch1
+	xor a
+	ld [wCurChannel], a ; just
+	ld [wSoundOutput], a ; off
+	ld bc, wChannel1
+.loop
+	; is the channel active?
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_CHANNEL_ON, [hl]
+	jp z, .nextchannel
+	; check time left in the current note
+	ld hl, CHANNEL_NOTE_DURATION
+	add hl, bc
+	ld a, [hl]
+	cp $2 ; 1 or 0?
+	jr c, .noteover
+	dec [hl]
+	jr .continue_sound_update
+
+.noteover
+	; reset vibrato delay
+	ld hl, CHANNEL_VIBRATO_DELAY
+	add hl, bc
+	ld a, [hl]
+	ld hl, CHANNEL_VIBRATO_DELAY_COUNT
+	add hl, bc
+	ld [hl], a
+	; turn vibrato off for now
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	res SOUND_PITCH_WHEEL, [hl]
+	; get next note
+	call ParseMusic
+.continue_sound_update
+	call ApplyPitchWheel
+	; duty cycle
+	ld hl, CHANNEL_DUTY_CYCLE
+	add hl, bc
+	ld a, [hli]
+	ld [wCurTrackDuty], a
+	; intensity
+	ld a, [hli]
+	ld [wCurTrackIntensity], a
+	; frequency
+	ld a, [hli]
+	ld [wCurTrackFrequency], a
+	ld a, [hl]
+	ld [wCurTrackFrequency + 1], a
+	; vibrato, noise
+	call HandleTrackVibrato ; handle vibrato and other things
+	call HandleNoise
+	; turn off music when playing sfx?
+	ld a, [wSFXPriority]
+	and a
+	jr z, .next
+	; are we in a sfx channel right now?
+	ld a, [wCurChannel]
+	cp NUM_MUSIC_CHANS
+	jr nc, .next
+	; are any sfx channels active?
+	; if so, mute
+	ld hl, wChannel5Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .restnote
+	ld hl, wChannel6Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .restnote
+	ld hl, wChannel7Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .restnote
+	ld hl, wChannel8Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr z, .next
+.restnote
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_REST, [hl] ; Rest
+.next
+	; are we in a sfx channel right now?
+	ld a, [wCurChannel]
+	cp NUM_MUSIC_CHANS
+	jr nc, .sfx_channel
+	ld hl, CHANNEL_STRUCT_LENGTH * NUM_MUSIC_CHANS + CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .sound_channel_on
+.sfx_channel
+	call UpdateChannels
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	ld a, [wSoundOutput]
+	or [hl]
+	ld [wSoundOutput], a
+.sound_channel_on
+	; clear note flags
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	xor a
+	ld [hl], a
+.nextchannel
+	; next channel
+	ld hl, CHANNEL_STRUCT_LENGTH
+	add hl, bc
+	ld c, l
+	ld b, h
+	ld a, [wCurChannel]
+	inc a
+	ld [wCurChannel], a
+	cp NUM_CHANNELS ; are we done?
+	jp nz, .loop ; do it all again
+
+	call PlayDanger
+	; fade music in/out
+	call FadeMusic
+	; write volume to hardware register
+	ld a, [wVolume]
+	ldh [rNR50], a
+	; write SO on/off to hardware register
+	ld a, [wSoundOutput]
+	ldh [rNR51], a
+	ret
+
+UpdateChannels:
+	ld hl, .ChannelFnPtrs
+	ld a, [wCurChannel]
+	and $7
+	add a
+	ld e, a
+	ld d, 0
+	add hl, de
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	jp hl
+
+.ChannelFnPtrs:
+	dw .Channel1
+	dw .Channel2
+	dw .Channel3
+	dw .Channel4
+; sfx ch ptrs are identical to music chs
+; ..except 5
+	dw .Channel5
+	dw .Channel6
+	dw .Channel7
+	dw .Channel8
+
+.Channel1:
+	ld a, [wLowHealthAlarm]
+	bit DANGER_ON_F, a
+	ret nz
+.Channel5:
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	bit NOTE_UNKN_3, [hl]
+	jr z, .asm_e8159
+	;
+	ld a, [wSoundInput]
+	ldh [rNR10], a
+.asm_e8159
+	bit NOTE_REST, [hl] ; rest
+	jr nz, .ch1rest
+	bit NOTE_NOISE_SAMPLING, [hl]
+	jr nz, .asm_e81a2
+	bit NOTE_FREQ_OVERRIDE, [hl]
+	jr nz, .frequency_override
+	bit NOTE_VIBRATO_OVERRIDE, [hl]
+	jr nz, .asm_e8184
+	jr .check_duty_override
+
+.frequency_override
+	ld a, [wCurTrackFrequency]
+	ldh [rNR13], a
+	ld a, [wCurTrackFrequency + 1]
+	ldh [rNR14], a
+.check_duty_override
+	bit NOTE_DUTY_OVERRIDE, [hl]
+	ret z
+	ld a, [wCurTrackDuty]
+	ld d, a
+	ldh a, [rNR11]
+	and $3f ; sound length
+	or d
+	ldh [rNR11], a
+	ret
+
+.asm_e8184
+	ld a, [wCurTrackDuty]
+	ld d, a
+	ldh a, [rNR11]
+	and $3f ; sound length
+	or d
+	ldh [rNR11], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR13], a
+	ret
+
+.ch1rest
+	ldh a, [rNR52]
+	and %10001110 ; ch1 off
+	ldh [rNR52], a
+	ld hl, rNR10
+	call ClearChannel
+	ret
+
+.asm_e81a2
+	ld hl, wCurTrackDuty
+	ld a, $3f ; sound length
+	or [hl]
+	ldh [rNR11], a
+	ld a, [wCurTrackIntensity]
+	ldh [rNR12], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR13], a
+	ld a, [wCurTrackFrequency + 1]
+	or $80
+	ldh [rNR14], a
+	ret
+
+.Channel2:
+.Channel6:
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	bit NOTE_REST, [hl] ; rest
+	jr nz, .ch2rest
+	bit NOTE_NOISE_SAMPLING, [hl]
+	jr nz, .asm_e8204
+	bit NOTE_VIBRATO_OVERRIDE, [hl]
+	jr nz, .asm_e81e6
+	bit NOTE_DUTY_OVERRIDE, [hl]
+	ret z
+	ld a, [wCurTrackDuty]
+	ld d, a
+	ldh a, [rNR21]
+	and $3f ; sound length
+	or d
+	ldh [rNR21], a
+	ret
+
+.asm_e81db ; unused
+	ld a, [wCurTrackFrequency]
+	ldh [rNR23], a
+	ld a, [wCurTrackFrequency + 1]
+	ldh [rNR24], a
+	ret
+
+.asm_e81e6
+	ld a, [wCurTrackDuty]
+	ld d, a
+	ldh a, [rNR21]
+	and $3f ; sound length
+	or d
+	ldh [rNR21], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR23], a
+	ret
+
+.ch2rest
+	ldh a, [rNR52]
+	and %10001101 ; ch2 off
+	ldh [rNR52], a
+	ld hl, rNR20
+	call ClearChannel
+	ret
+
+.asm_e8204
+	ld hl, wCurTrackDuty
+	ld a, $3f ; sound length
+	or [hl]
+	ldh [rNR21], a
+	ld a, [wCurTrackIntensity]
+	ldh [rNR22], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR23], a
+	ld a, [wCurTrackFrequency + 1]
+	or $80 ; initial (restart)
+	ldh [rNR24], a
+	ret
+
+.Channel3:
+.Channel7:
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	bit NOTE_REST, [hl] ; rest
+	jr nz, .ch3rest
+	bit NOTE_NOISE_SAMPLING, [hl]
+	jr nz, .asm_e824d
+	bit NOTE_VIBRATO_OVERRIDE, [hl]
+	jr nz, .asm_e823a
+	ret
+
+.asm_e822f ; unused
+	ld a, [wCurTrackFrequency]
+	ldh [rNR33], a
+	ld a, [wCurTrackFrequency + 1]
+	ldh [rNR34], a
+	ret
+
+.asm_e823a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR33], a
+	ret
+
+.ch3rest
+	ldh a, [rNR52]
+	and %10001011 ; ch3 off
+	ldh [rNR52], a
+	ld hl, rNR30
+	call ClearChannel
+	ret
+
+.asm_e824d
+	ld a, $3f ; sound length
+	ldh [rNR31], a
+	xor a
+	ldh [rNR30], a
+	call .asm_e8268
+	ld a, $80
+	ldh [rNR30], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR33], a
+	ld a, [wCurTrackFrequency + 1]
+	or $80
+	ldh [rNR34], a
+	ret
+
+.asm_e8268
+	push hl
+	ld a, [wCurTrackIntensity]
+	and $f ; only 0-9 are valid
+	ld l, a
+	ld h, 0
+	; hl << 4
+	; each wavepattern is $f bytes long
+	; so seeking is done in $10s
+rept 4
+	add hl, hl
+endr
+	ld de, WaveSamples
+	add hl, de
+	; load wavepattern into rWave_0-rWave_f
+	ld a, [hli]
+	ldh [rWave_0], a
+	ld a, [hli]
+	ldh [rWave_1], a
+	ld a, [hli]
+	ldh [rWave_2], a
+	ld a, [hli]
+	ldh [rWave_3], a
+	ld a, [hli]
+	ldh [rWave_4], a
+	ld a, [hli]
+	ldh [rWave_5], a
+	ld a, [hli]
+	ldh [rWave_6], a
+	ld a, [hli]
+	ldh [rWave_7], a
+	ld a, [hli]
+	ldh [rWave_8], a
+	ld a, [hli]
+	ldh [rWave_9], a
+	ld a, [hli]
+	ldh [rWave_a], a
+	ld a, [hli]
+	ldh [rWave_b], a
+	ld a, [hli]
+	ldh [rWave_c], a
+	ld a, [hli]
+	ldh [rWave_d], a
+	ld a, [hli]
+	ldh [rWave_e], a
+	ld a, [hli]
+	ldh [rWave_f], a
+	pop hl
+	ld a, [wCurTrackIntensity]
+	and $f0
+	sla a
+	ldh [rNR32], a
+	ret
+
+.Channel4:
+.Channel8:
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	bit NOTE_REST, [hl] ; rest
+	jr nz, .ch4rest
+	bit NOTE_NOISE_SAMPLING, [hl]
+	jr nz, .asm_e82d4
+	ret
+
+.asm_e82c1 ; unused
+	ld a, [wCurTrackFrequency]
+	ldh [rNR43], a
+	ret
+
+.ch4rest
+	ldh a, [rNR52]
+	and %10000111 ; ch4 off
+	ldh [rNR52], a
+	ld hl, rNR40
+	call ClearChannel
+	ret
+
+.asm_e82d4
+	ld a, $3f ; sound length
+	ldh [rNR41], a
+	ld a, [wCurTrackIntensity]
+	ldh [rNR42], a
+	ld a, [wCurTrackFrequency]
+	ldh [rNR43], a
+	ld a, $80
+	ldh [rNR44], a
+	ret
+
+_CheckSFX:
+; return carry if any sfx channels are active
+	ld hl, wChannel5Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .sfxon
+	ld hl, wChannel6Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .sfxon
+	ld hl, wChannel7Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .sfxon
+	ld hl, wChannel8Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .sfxon
+	and a
+	ret
+
+.sfxon
+	scf
+	ret
+
+PlayDanger:
+	ld a, [wLowHealthAlarm]
+	bit DANGER_ON_F, a
+	ret z
+
+	; Don't do anything if SFX is being played
+	and $ff ^ (1 << DANGER_ON_F)
+	ld d, a
+	call _CheckSFX
+	jr c, .increment
+
+	; Play the high tone
+	and a
+	jr z, .begin
+
+	; Play the low tone
+	cp 16
+	jr z, .halfway
+
+	jr .increment
+
+.halfway
+	ld hl, DangerSoundLow
+	jr .applychannel
+
+.begin
+	ld hl, DangerSoundHigh
+
+.applychannel
+	xor a
+	ldh [rNR10], a
+	ld a, [hli]
+	ldh [rNR11], a
+	ld a, [hli]
+	ldh [rNR12], a
+	ld a, [hli]
+	ldh [rNR13], a
+	ld a, [hli]
+	ldh [rNR14], a
+
+.increment
+	ld a, d
+	inc a
+	cp 30 ; Ending frame
+	jr c, .noreset
+	xor a
+.noreset
+	; Make sure the danger sound is kept on
+	or 1 << DANGER_ON_F
+	ld [wLowHealthAlarm], a
+
+	; Enable channel 1 if it's off
+	ld a, [wSoundOutput]
+	and $11
+	ret nz
+	ld a, [wSoundOutput]
+	or $11
+	ld [wSoundOutput], a
+	ret
+
+DangerSoundHigh:
+	db $80 ; duty 50%
+	db $e2 ; volume 14, envelope decrease sweep 2
+	db $50 ; frequency: $750
+	db $87 ; restart sound
+
+DangerSoundLow:
+	db $80 ; duty 50%
+	db $e2 ; volume 14, envelope decrease sweep 2
+	db $ee ; frequency: $6ee
+	db $86 ; restart sound
+
+FadeMusic:
+; fade music if applicable
+; usage:
+;	write to wMusicFade
+;	song fades out at the given rate
+;	load song id in wMusicFadeID
+;	fade new song in
+; notes:
+;	max # frames per volume level is $3f
+
+	; fading?
+	ld a, [wMusicFade]
+	and a
+	ret z
+	; has the count ended?
+	ld a, [wMusicFadeCount]
+	and a
+	jr z, .update
+	; count down
+	dec a
+	ld [wMusicFadeCount], a
+	ret
+
+.update
+	ld a, [wMusicFade]
+	ld d, a
+	; get new count
+	and $3f
+	ld [wMusicFadeCount], a
+	; get SO1 volume
+	ld a, [wVolume]
+	and VOLUME_SO1_LEVEL
+	; which way are we fading?
+	bit MUSIC_FADE_IN_F, d
+	jr nz, .fadein
+	; fading out
+	and a
+	jr z, .novolume
+	dec a
+	jr .updatevolume
+
+.novolume
+	; make sure volume is off
+	xor a
+	ld [wVolume], a
+	; did we just get on a bike?
+	ld a, [wPlayerState]
+	cp PLAYER_BIKE
+	jr z, .bicycle
+	push bc
+	; restart sound
+	call MusicFadeRestart
+	; get new song id
+	ld a, [wMusicFadeID]
+	and a
+	jr z, .quit ; this assumes there are fewer than 256 songs!
+	ld e, a
+	ld a, [wMusicFadeID + 1]
+	ld d, a
+	; load new song
+	call _PlayMusic
+.quit
+	; cleanup
+	pop bc
+	; stop fading
+	xor a
+	ld [wMusicFade], a
+	ret
+
+.bicycle
+	push bc
+	; restart sound
+	call MusicFadeRestart
+	; this turns the volume up
+	; turn it back down
+	xor a
+	ld [wVolume], a
+	; get new song id
+	ld a, [wMusicFadeID]
+	ld e, a
+	ld a, [wMusicFadeID + 1]
+	ld d, a
+	; load new song
+	call _PlayMusic
+	pop bc
+	; fade in
+	ld hl, wMusicFade
+	set MUSIC_FADE_IN_F, [hl]
+	ret
+
+.fadein
+	; are we done?
+	cp MAX_VOLUME & $f
+	jr nc, .maxvolume
+	; inc volume
+	inc a
+	jr .updatevolume
+
+.maxvolume
+	; we're done
+	xor a
+	ld [wMusicFade], a
+	ret
+
+.updatevolume
+	; hi = lo
+	ld d, a
+	swap a
+	or d
+	ld [wVolume], a
+	ret
+
+LoadNote:
+	; wait for pitch wheel to finish
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	bit SOUND_PITCH_WHEEL, [hl]
+	ret z
+	; get note duration
+	ld hl, CHANNEL_NOTE_DURATION
+	add hl, bc
+	ld a, [hl]
+	ld hl, wCurNoteDuration
+	sub [hl]
+	jr nc, .ok
+	ld a, 1
+.ok
+	ld [hl], a
+	; get frequency
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; get direction of pitch wheel
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld a, e
+	sub [hl]
+	ld e, a
+	ld a, d
+	sbc 0
+	ld d, a
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	sub [hl]
+	jr nc, .greater_than
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	set SOUND_PITCH_WHEEL_DIR, [hl]
+	; get frequency
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; ????
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld a, [hl]
+	sub e
+	ld e, a
+	ld a, d
+	sbc 0
+	ld d, a
+	; ????
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	ld a, [hl]
+	sub d
+	ld d, a
+	jr .resume
+
+.greater_than
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	res SOUND_PITCH_WHEEL_DIR, [hl]
+	; get frequency
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; get distance from pitch wheel target
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld a, e
+	sub [hl]
+	ld e, a
+	ld a, d
+	sbc 0
+	ld d, a
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	sub [hl]
+	ld d, a
+.resume
+	; de = x * [wCurNoteDuration] + y
+	; x + 1 -> d
+	; y -> a
+	push bc
+	ld hl, wCurNoteDuration
+	ld b, 0 ; quotient
+.loop
+	inc b
+	ld a, e
+	sub [hl]
+	ld e, a
+	jr nc, .loop
+	ld a, d
+	and a
+	jr z, .quit
+	dec d
+	jr .loop
+
+.quit
+	ld a, e ; remainder
+	add [hl]
+	ld d, b ; quotient
+	pop bc
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT
+	add hl, bc
+	ld [hl], d ; quotient
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT_FRACTION
+	add hl, bc
+	ld [hl], a ; remainder
+	ld hl, CHANNEL_FIELD25
+	add hl, bc
+	xor a
+	ld [hl], a
+	ret
+
+HandleTrackVibrato:
+; handle duty, cry pitch, and vibrato
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	bit SOUND_DUTY, [hl] ; duty
+	jr z, .next
+	ld hl, CHANNEL_SFX_DUTY_LOOP
+	add hl, bc
+	ld a, [hl]
+	rlca
+	rlca
+	ld [hl], a
+	and $c0
+	ld [wCurTrackDuty], a
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_DUTY_OVERRIDE, [hl]
+.next
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	bit SOUND_CRY_PITCH, [hl]
+	jr z, .vibrato
+	ld hl, CHANNEL_CRY_PITCH
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	ld hl, wCurTrackFrequency
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	add hl, de
+	ld e, l
+	ld d, h
+	ld hl, wCurTrackFrequency
+	ld [hl], e
+	inc hl
+	ld [hl], d
+.vibrato
+	; is vibrato on?
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	bit SOUND_VIBRATO, [hl] ; vibrato
+	jr z, .quit
+	; is vibrato active for this note yet?
+	; is the delay over?
+	ld hl, CHANNEL_VIBRATO_DELAY_COUNT
+	add hl, bc
+	ld a, [hl]
+	and a
+	jr nz, .subexit
+	; is the extent nonzero?
+	ld hl, CHANNEL_VIBRATO_EXTENT
+	add hl, bc
+	ld a, [hl]
+	and a
+	jr z, .quit
+	; save it for later
+	ld d, a
+	; is it time to toggle vibrato up/down?
+	ld hl, CHANNEL_VIBRATO_RATE
+	add hl, bc
+	ld a, [hl]
+	and $f ; count
+	jr z, .toggle
+.subexit
+	dec [hl]
+	jr .quit
+
+.toggle
+	; refresh count
+	ld a, [hl]
+	swap [hl]
+	or [hl]
+	ld [hl], a
+	; ????
+	ld a, [wCurTrackFrequency]
+	ld e, a
+	; toggle vibrato up/down
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	bit SOUND_VIBRATO_DIR, [hl] ; vibrato up/down
+	jr z, .down
+; up
+	; vibrato down
+	res SOUND_VIBRATO_DIR, [hl]
+	; get the delay
+	ld a, d
+	and $f ; lo
+	;
+	ld d, a
+	ld a, e
+	sub d
+	jr nc, .no_carry
+	ld a, 0
+	jr .no_carry
+
+.down
+	; vibrato up
+	set SOUND_VIBRATO_DIR, [hl]
+	; get the delay
+	ld a, d
+	and $f0 ; hi
+	swap a ; move it to lo
+	;
+	add e
+	jr nc, .no_carry
+	ld a, $ff
+.no_carry
+	ld [wCurTrackFrequency], a
+	;
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_VIBRATO_OVERRIDE, [hl]
+.quit
+	ret
+
+ApplyPitchWheel:
+	; quit if pitch wheel inactive
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	bit SOUND_PITCH_WHEEL, [hl]
+	ret z
+	; de = Frequency
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; check whether pitch wheel is going up or down
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	bit SOUND_PITCH_WHEEL_DIR, [hl]
+	jr z, .decreasing
+	; frequency += [Channel*PitchWheelAmount]
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT
+	add hl, bc
+	ld l, [hl]
+	ld h, 0
+	add hl, de
+	ld d, h
+	ld e, l
+	; [Channel*Field25] += [Channel*PitchWheelAmountFraction]
+	; if rollover: Frequency += 1
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT_FRACTION
+	add hl, bc
+	ld a, [hl]
+	ld hl, CHANNEL_FIELD25
+	add hl, bc
+	add [hl]
+	ld [hl], a
+	ld a, 0
+	adc e
+	ld e, a
+	ld a, 0
+	adc d
+	ld d, a
+	; Compare the dw at [Channel*PitchWheelTarget] to de.
+	; If frequency is greater, we're finished.
+	; Otherwise, load the frequency and set two flags.
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	ld a, [hl]
+	cp d
+	jp c, .finished_pitch_wheel
+	jr nz, .continue_pitch_wheel
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld a, [hl]
+	cp e
+	jp c, .finished_pitch_wheel
+	jr .continue_pitch_wheel
+
+.decreasing
+	; frequency -= [Channel*PitchWheelAmount]
+	ld a, e
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT
+	add hl, bc
+	ld e, [hl]
+	sub e
+	ld e, a
+	ld a, d
+	sbc 0
+	ld d, a
+	; [Channel*Field25] *= 2
+	; if rollover: Frequency -= 1
+	ld hl, CHANNEL_PITCH_WHEEL_AMOUNT_FRACTION
+	add hl, bc
+	ld a, [hl]
+	add a
+	ld [hl], a
+	ld a, e
+	sbc 0
+	ld e, a
+	ld a, d
+	sbc 0
+	ld d, a
+	; Compare the dw at [Channel*PitchWheelTarget] to de.
+	; If frequency is lower, we're finished.
+	; Otherwise, load the frequency and set two flags.
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	ld a, d
+	cp [hl]
+	jr c, .finished_pitch_wheel
+	jr nz, .continue_pitch_wheel
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld a, e
+	cp [hl]
+	jr nc, .continue_pitch_wheel
+.finished_pitch_wheel
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	res SOUND_PITCH_WHEEL, [hl]
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	res SOUND_PITCH_WHEEL_DIR, [hl]
+	ret
+
+.continue_pitch_wheel
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_FREQ_OVERRIDE, [hl]
+	set NOTE_DUTY_OVERRIDE, [hl]
+	ret
+
+HandleNoise:
+	; is noise sampling on?
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_NOISE, [hl] ; noise sampling
+	ret z
+	; are we in a sfx channel?
+	ld a, [wCurChannel]
+	bit NOISE_CHAN_F, a
+	jr nz, .next
+	; is ch8 on? (noise)
+	ld hl, wChannel8Flags1
+	bit SOUND_CHANNEL_ON, [hl] ; on?
+	jr z, .next
+	; is ch8 playing noise?
+	bit SOUND_NOISE, [hl]
+	ret nz ; quit if so
+	;
+.next
+	ld a, [wNoiseSampleDelay]
+	and a
+	jr z, ReadNoiseSample
+	dec a
+	ld [wNoiseSampleDelay], a
+	ret
+
+ReadNoiseSample:
+; sample struct:
+;	[wx] [yy] [zz]
+;	w: ? either 2 or 3
+;	x: duration
+;	zz: intensity
+;       yy: frequency
+
+	; de = [wNoiseSampleAddress]
+	ld hl, wNoiseSampleAddress
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+
+	; is it empty?
+	ld a, e
+	or d
+	jr z, .quit
+
+	ld a, [de]
+	inc de
+
+	cp endchannel_cmd
+	jr z, .quit
+
+	and $f
+	inc a
+	ld [wNoiseSampleDelay], a
+	ld a, [de]
+	inc de
+	ld [wCurTrackIntensity], a
+	ld a, [de]
+	inc de
+	ld [wCurTrackFrequency], a
+	xor a
+	ld [wCurTrackFrequency + 1], a
+
+	ld hl, wNoiseSampleAddress
+	ld [hl], e
+	inc hl
+	ld [hl], d
+
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_NOISE_SAMPLING, [hl]
+	ret
+
+.quit
+	ret
+
+ParseMusic:
+; parses until a note is read or the song is ended
+	call GetMusicByte ; store next byte in a
+	cp endchannel_cmd
+	jr z, .endchannel
+	cp FIRST_MUSIC_CMD
+	jr c, .readnote
+	; then it's a command
+.readcommand
+	call ParseMusicCommand
+	jr ParseMusic ; start over
+
+.readnote
+; wCurMusicByte contains current note
+; special notes
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_SFX, [hl]
+	jp nz, ParseSFXOrRest
+	bit SOUND_REST, [hl] ; rest
+	jp nz, ParseSFXOrRest
+	bit SOUND_NOISE, [hl] ; noise sample
+	jp nz, GetNoiseSample
+; normal note
+	; set note duration (bottom nybble)
+	ld a, [wCurMusicByte]
+	and $f
+	call SetNoteDuration
+	; get note pitch (top nybble)
+	ld a, [wCurMusicByte]
+	swap a
+	and $f
+	jr z, .rest ; pitch 0-> rest
+	; update pitch
+	ld hl, CHANNEL_PITCH
+	add hl, bc
+	ld [hl], a
+	; store pitch in e
+	ld e, a
+	; store octave in d
+	ld hl, CHANNEL_OCTAVE
+	add hl, bc
+	ld d, [hl]
+	; update frequency
+	call GetFrequency
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	; ????
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_NOISE_SAMPLING, [hl]
+	jp LoadNote
+
+.rest
+; note = rest
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_REST, [hl] ; Rest
+	ret
+
+.endchannel
+; $ff is reached in music data
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_SUBROUTINE, [hl] ; in a subroutine?
+	jr nz, .readcommand ; execute
+	ld a, [wCurChannel]
+	cp CHAN5
+	jr nc, .chan_5to8
+	; ????
+	ld hl, CHANNEL_STRUCT_LENGTH * NUM_MUSIC_CHANS + CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_CHANNEL_ON, [hl]
+	jr nz, .ok
+.chan_5to8
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_REST, [hl]
+	call nz, RestoreVolume
+	; end music
+	ld a, [wCurChannel]
+	cp CHAN5
+	jr nz, .ok
+	; ????
+	xor a
+	ldh [rNR10], a ; sweep = 0
+.ok
+; stop playing
+	; turn channel off
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	res SOUND_CHANNEL_ON, [hl]
+	; note = rest
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_REST, [hl]
+	; clear music id & bank
+	ld hl, CHANNEL_MUSIC_ID
+	add hl, bc
+	xor a
+	ld [hli], a ; id hi
+	ld [hli], a ; id lo
+	ld [hli], a ; bank
+	ret
+
+RestoreVolume:
+	; ch5 only
+	ld a, [wCurChannel]
+	cp CHAN5
+	ret nz
+	xor a
+	ld hl, wChannel6CryPitch
+	ld [hli], a
+	ld [hl], a
+	ld hl, wChannel8CryPitch
+	ld [hli], a
+	ld [hl], a
+	ld a, [wLastVolume]
+	ld [wVolume], a
+	xor a
+	ld [wLastVolume], a
+	ld [wSFXPriority], a
+	ret
+
+ParseSFXOrRest:
+	; turn noise sampling on
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_NOISE_SAMPLING, [hl] ; noise sample
+	; update note duration
+	ld a, [wCurMusicByte]
+	call SetNoteDuration ; top nybble doesnt matter?
+	; update intensity from next param
+	call GetMusicByte
+	ld hl, CHANNEL_INTENSITY
+	add hl, bc
+	ld [hl], a
+	; update lo frequency from next param
+	call GetMusicByte
+	ld hl, CHANNEL_FREQUENCY
+	add hl, bc
+	ld [hl], a
+	; are we on the last channel? (noise sampling)
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	cp CHAN4
+	ret z
+	; update hi frequency from next param
+	call GetMusicByte
+	ld hl, CHANNEL_FREQUENCY + 1
+	add hl, bc
+	ld [hl], a
+	ret
+
+GetNoiseSample:
+; load ptr to sample header in wNoiseSampleAddress
+	; are we on the last channel?
+	ld a, [wCurChannel]
+	and NUM_MUSIC_CHANS + -1
+	cp CHAN4
+	; ret if not
+	ret nz
+	; update note duration
+	ld a, [wCurMusicByte]
+	and $f
+	call SetNoteDuration
+	; check current channel
+	ld a, [wCurChannel]
+	bit NOISE_CHAN_F, a
+	jr nz, .sfx
+	ld hl, wChannel8Flags1
+	bit SOUND_CHANNEL_ON, [hl] ; is ch8 on? (noise)
+	ret nz
+	ld a, [wMusicNoiseSampleSet]
+	jr .next
+
+.sfx
+	ld a, [wSFXNoiseSampleSet]
+.next
+	; load noise sample set id into de
+	ld e, a
+	ld d, 0
+	; load ptr to noise sample set in hl
+	ld hl, Drumkits
+	add hl, de
+	add hl, de
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	; get pitch
+	ld a, [wCurMusicByte]
+	swap a
+	; non-rest note?
+	and $f
+	ret z
+	; use 'pitch' to seek noise sample set
+	ld e, a
+	ld d, 0
+	add hl, de
+	add hl, de
+	; load sample pointer into wNoiseSampleAddress
+	ld a, [hli]
+	ld [wNoiseSampleAddress], a
+	ld a, [hl]
+	ld [wNoiseSampleAddress + 1], a
+	; clear ????
+	xor a
+	ld [wNoiseSampleDelay], a
+	ret
+
+ParseMusicCommand:
+	; reload command
+	ld a, [wCurMusicByte]
+	; get command #
+	sub FIRST_MUSIC_CMD
+	ld e, a
+	ld d, 0
+	; seek command pointer
+	ld hl, MusicCommands
+	add hl, de
+	add hl, de
+	; jump to the new pointer
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	jp hl
+
+MusicCommands:
+; entries correspond to macros/sound.asm enumeration
+	dw Music_Octave8 ; octave 8
+	dw Music_Octave7 ; octave 7
+	dw Music_Octave6 ; octave 6
+	dw Music_Octave5 ; octave 5
+	dw Music_Octave4 ; octave 4
+	dw Music_Octave3 ; octave 3
+	dw Music_Octave2 ; octave 2
+	dw Music_Octave1 ; octave 1
+	dw Music_NoteType ; note length + intensity
+	dw Music_ForceOctave ; set starting octave
+	dw Music_Tempo ; tempo
+	dw Music_DutyCycle ; duty cycle
+	dw Music_Intensity ; intensity
+	dw Music_SoundStatus ; update sound status
+	dw Music_SoundDuty ; sfx duty
+	dw Music_ToggleSFX ; sound on/off
+	dw Music_SlidePitchTo ; pitch wheel
+	dw Music_Vibrato ; vibrato
+	dw MusicE2 ; unused
+	dw Music_ToggleNoise ; music noise sampling
+	dw Music_Panning ; force panning
+	dw Music_Volume ; volume
+	dw Music_Tone ; tone
+	dw MusicE7 ; unused
+	dw MusicE8 ; unused
+	dw Music_TempoRelative ; global tempo
+	dw Music_RestartChannel ; restart current channel from header
+	dw Music_NewSong ; new song
+	dw Music_SFXPriorityOn ; sfx priority on
+	dw Music_SFXPriorityOff ; sfx priority off
+	dw MusicEE ; unused
+	dw Music_StereoPanning ; stereo panning
+	dw Music_SFXToggleNoise ; sfx noise sampling
+	dw MusicF1 ; nothing
+	dw MusicF2 ; nothing
+	dw MusicF3 ; nothing
+	dw MusicF4 ; nothing
+	dw MusicF5 ; nothing
+	dw MusicF6 ; nothing
+	dw MusicF7 ; nothing
+	dw MusicF8 ; nothing
+	dw MusicF9 ; unused
+	dw Music_SetCondition ; setcondition
+	dw Music_JumpIf ; jumpif
+	dw Music_JumpChannel ; jump
+	dw Music_LoopChannel ; loop
+	dw Music_CallChannel ; call
+	dw Music_EndChannel ; return
+
+MusicF1:
+MusicF2:
+MusicF3:
+MusicF4:
+MusicF5:
+MusicF6:
+MusicF7:
+MusicF8:
+	ret
+
+Music_EndChannel:
+; called when $ff is encountered w/ subroutine flag set
+; end music stream
+; return to caller of the subroutine
+	; reset subroutine flag
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	res SOUND_SUBROUTINE, [hl]
+	; copy LastMusicAddress to MusicAddress
+	ld hl, CHANNEL_LAST_MUSIC_ADDRESS
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ret
+
+Music_CallChannel:
+; call music stream (subroutine)
+; parameters: ll hh ; pointer to subroutine
+	; get pointer from next 2 bytes
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	push de
+	; copy MusicAddress to LastMusicAddress
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	ld hl, CHANNEL_LAST_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	; load pointer into MusicAddress
+	pop de
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	; set subroutine flag
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_SUBROUTINE, [hl]
+	ret
+
+Music_JumpChannel:
+; jump
+; parameters: ll hh ; pointer
+	; get pointer from next 2 bytes
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ret
+
+Music_LoopChannel:
+; loops xx - 1 times
+; 	00: infinite
+; params: 3
+;	xx ll hh
+;		xx : loop count
+;   	ll hh : pointer
+
+	; get loop count
+	call GetMusicByte
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_LOOPING, [hl] ; has the loop been initiated?
+	jr nz, .checkloop
+	and a ; loop counter 0 = infinite
+	jr z, .loop
+	; initiate loop
+	dec a
+	set SOUND_LOOPING, [hl] ; set loop flag
+	ld hl, CHANNEL_LOOP_COUNT
+	add hl, bc
+	ld [hl], a ; store loop counter
+.checkloop
+	ld hl, CHANNEL_LOOP_COUNT
+	add hl, bc
+	ld a, [hl]
+	and a ; are we done?
+	jr z, .endloop
+	dec [hl]
+.loop
+	; get pointer
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	; load new pointer into MusicAddress
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ret
+
+.endloop
+	; reset loop flag
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	res SOUND_LOOPING, [hl]
+	; skip to next command
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	inc de ; skip
+	inc de ; pointer
+	ld [hl], d
+	dec hl
+	ld [hl], e
+	ret
+
+Music_SetCondition:
+; set condition for a jump
+; used with FB
+; params: 1
+;	xx ; condition
+
+	; set condition
+	call GetMusicByte
+	ld hl, CHANNEL_CONDITION
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_JumpIf:
+; conditional jump
+; used with FA
+; params: 3
+; 	xx: condition
+;	ll hh: pointer
+
+; check condition
+	; a = condition
+	call GetMusicByte
+	; if existing condition matches, jump to new address
+	ld hl, CHANNEL_CONDITION
+	add hl, bc
+	cp [hl]
+	jr z, .jump
+; skip to next command
+	; get address
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; skip pointer
+	inc de
+	inc de
+	; update address
+	ld [hl], d
+	dec hl
+	ld [hl], e
+	ret
+
+.jump
+; jump to the new address
+	; get pointer
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	; update pointer in MusicAddress
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ret
+
+MusicEE:
+; conditional jump
+; checks a byte in ram corresponding to the current channel
+; doesn't seem to be set by any commands
+; params: 2
+;		ll hh ; pointer
+
+; if ????, jump
+	; get channel
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	ld e, a
+	ld d, 0
+	; hl = wChannel1JumpCondition + channel id
+	ld hl, wChannel1JumpCondition
+	add hl, de
+	; if set, jump
+	ld a, [hl]
+	and a
+	jr nz, .jump
+; skip to next command
+	; get address
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; skip pointer
+	inc de
+	inc de
+	; update address
+	ld [hl], d
+	dec hl
+	ld [hl], e
+	ret
+
+.jump
+	; reset jump flag
+	ld [hl], 0
+	; de = pointer
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	; update address
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ret
+
+MusicF9:
+; sets some flag
+; seems to be unused
+; params: 0
+	ld a, TRUE
+	ld [wUnusedMusicF9Flag], a
+	ret
+
+MusicE2:
+; seems to have been dummied out
+; params: 1
+	call GetMusicByte
+	ld hl, CHANNEL_FIELD2C
+	add hl, bc
+	ld [hl], a
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_UNKN_0B, [hl]
+	ret
+
+Music_Vibrato:
+; vibrato
+; params: 2
+;	1: [xx]
+	; delay in frames
+;	2: [yz]
+	; y: extent
+	; z: rate (# frames per cycle)
+
+	; set vibrato flag?
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_VIBRATO, [hl]
+	; start at lower frequency (extent is positive)
+	ld hl, CHANNEL_FLAGS3
+	add hl, bc
+	res SOUND_VIBRATO_DIR, [hl]
+	; get delay
+	call GetMusicByte
+; update delay
+	ld hl, CHANNEL_VIBRATO_DELAY
+	add hl, bc
+	ld [hl], a
+; update delay count
+	ld hl, CHANNEL_VIBRATO_DELAY_COUNT
+	add hl, bc
+	ld [hl], a
+; update extent
+; this is split into halves only to get added back together at the last second
+	; get extent/rate
+	call GetMusicByte
+	ld hl, CHANNEL_VIBRATO_EXTENT
+	add hl, bc
+	ld d, a
+	; get top nybble
+	and $f0
+	swap a
+	srl a ; halve
+	ld e, a
+	adc 0 ; round up
+	swap a
+	or e
+	ld [hl], a
+; update rate
+	ld hl, CHANNEL_VIBRATO_RATE
+	add hl, bc
+	; get bottom nybble
+	ld a, d
+	and $f
+	ld d, a
+	swap a
+	or d
+	ld [hl], a
+	ret
+
+Music_SlidePitchTo:
+; set the target for pitch wheel
+; params: 2
+; note duration
+; target note
+	call GetMusicByte
+	ld [wCurNoteDuration], a
+
+	call GetMusicByte
+	; pitch in e
+	ld d, a
+	and $f
+	ld e, a
+
+	; octave in d
+	ld a, d
+	swap a
+	and $f
+	ld d, a
+	call GetFrequency
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET
+	add hl, bc
+	ld [hl], e
+	ld hl, CHANNEL_PITCH_WHEEL_TARGET + 1
+	add hl, bc
+	ld [hl], d
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_PITCH_WHEEL, [hl]
+	ret
+
+Music_Tone:
+; tone
+; params: 1 (dw)
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_CRY_PITCH, [hl]
+	ld hl, CHANNEL_CRY_PITCH + 1
+	add hl, bc
+	call GetMusicByte
+	ld [hld], a
+	call GetMusicByte
+	ld [hl], a
+	ret
+
+MusicE7:
+; unused
+; params: 1
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_UNKN_0E, [hl]
+	call GetMusicByte
+	ld hl, CHANNEL_FIELD29
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_SoundDuty:
+; sequence of 4 duty cycles to be looped
+; params: 1 (4 2-bit duty cycle arguments)
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_DUTY, [hl] ; duty cycle
+	; sound duty sequence
+	call GetMusicByte
+	rrca
+	rrca
+	ld hl, CHANNEL_SFX_DUTY_LOOP
+	add hl, bc
+	ld [hl], a
+	; update duty cycle
+	and $c0 ; only uses top 2 bits
+	ld hl, CHANNEL_DUTY_CYCLE
+	add hl, bc
+	ld [hl], a
+	ret
+
+MusicE8:
+; unused
+; params: 1
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_UNKN_0D, [hl]
+	call GetMusicByte
+	ld hl, CHANNEL_FIELD2A
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_ToggleSFX:
+; toggle something
+; params: none
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_SFX, [hl]
+	jr z, .on
+	res SOUND_SFX, [hl]
+	ret
+
+.on
+	set SOUND_SFX, [hl]
+	ret
+
+Music_ToggleNoise:
+; toggle music noise sampling
+; can't be used as a straight toggle since the param is not read from on->off
+; params:
+; 	noise on: 1
+; 	noise off: 0
+	; check if noise sampling is on
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_NOISE, [hl]
+	jr z, .on
+	; turn noise sampling off
+	res SOUND_NOISE, [hl]
+	ret
+
+.on
+	; turn noise sampling on
+	set SOUND_NOISE, [hl]
+	call GetMusicByte
+	ld [wMusicNoiseSampleSet], a
+	ret
+
+Music_SFXToggleNoise:
+; toggle sfx noise sampling
+; params:
+;	on: 1
+; 	off: 0
+	; check if noise sampling is on
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	bit SOUND_NOISE, [hl]
+	jr z, .on
+	; turn noise sampling off
+	res SOUND_NOISE, [hl]
+	ret
+
+.on
+	; turn noise sampling on
+	set SOUND_NOISE, [hl]
+	call GetMusicByte
+	ld [wSFXNoiseSampleSet], a
+	ret
+
+Music_NoteType:
+; note length
+;	# frames per 16th note
+; intensity: see Music_Intensity
+; params: 2
+	; note length
+	call GetMusicByte
+	ld hl, CHANNEL_NOTE_LENGTH
+	add hl, bc
+	ld [hl], a
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	cp CHAN4
+	ret z
+	; intensity
+	call Music_Intensity
+	ret
+
+Music_SoundStatus:
+; update sound status
+; params: 1
+	call GetMusicByte
+	ld [wSoundInput], a
+	ld hl, CHANNEL_NOTE_FLAGS
+	add hl, bc
+	set NOTE_UNKN_3, [hl]
+	ret
+
+Music_DutyCycle:
+; duty cycle
+; params: 1
+	call GetMusicByte
+	rrca
+	rrca
+	and $c0
+	ld hl, CHANNEL_DUTY_CYCLE
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_Intensity:
+; intensity
+; params: 1
+;	hi: pressure
+;   lo: velocity
+	call GetMusicByte
+	ld hl, CHANNEL_INTENSITY
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_Tempo:
+; global tempo
+; params: 2
+;	de: tempo
+	call GetMusicByte
+	ld d, a
+	call GetMusicByte
+	ld e, a
+	call SetGlobalTempo
+	ret
+
+Music_Octave8:
+Music_Octave7:
+Music_Octave6:
+Music_Octave5:
+Music_Octave4:
+Music_Octave3:
+Music_Octave2:
+Music_Octave1:
+; set octave based on lo nybble of the command
+	ld hl, CHANNEL_OCTAVE
+	add hl, bc
+	ld a, [wCurMusicByte]
+	and 7
+	ld [hl], a
+	ret
+
+Music_ForceOctave:
+; set starting octave
+; this forces all notes up by the starting octave
+; params: 1
+	call GetMusicByte
+	ld hl, CHANNEL_PITCH_OFFSET
+	add hl, bc
+	ld [hl], a
+	ret
+
+Music_StereoPanning:
+; stereo panning
+; params: 1
+	; stereo on?
+	ld a, [wOptions]
+	bit STEREO, a
+	jr nz, Music_Panning
+	; skip param
+	call GetMusicByte
+	ret
+
+Music_Panning:
+; force panning
+; params: 1
+	call SetLRTracks
+	call GetMusicByte
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	and [hl]
+	ld [hl], a
+	ret
+
+Music_Volume:
+; set volume
+; params: 1
+;	see Volume
+	; read param even if it's not used
+	call GetMusicByte
+	; is the song fading?
+	ld a, [wMusicFade]
+	and a
+	ret nz
+	; reload param
+	ld a, [wCurMusicByte]
+	; set volume
+	ld [wVolume], a
+	ret
+
+Music_TempoRelative:
+; set global tempo to current channel tempo +/- param
+; params: 1 signed
+	call GetMusicByte
+	ld e, a
+	; check sign
+	cp $80
+	jr nc, .negative
+;positive
+	ld d, 0
+	jr .ok
+
+.negative
+	ld d, -1
+.ok
+	ld hl, CHANNEL_TEMPO
+	add hl, bc
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	add hl, de
+	ld e, l
+	ld d, h
+	call SetGlobalTempo
+	ret
+
+Music_SFXPriorityOn:
+; turn sfx priority on
+; params: none
+	ld a, 1
+	ld [wSFXPriority], a
+	ret
+
+Music_SFXPriorityOff:
+; turn sfx priority off
+; params: none
+	xor a
+	ld [wSFXPriority], a
+	ret
+
+Music_RestartChannel:
+; restart current channel from channel header (same bank)
+; params: 2 (5)
+; ll hh: pointer to new channel header
+;	header format: 0x yy zz
+;		x: channel # (0-3)
+;		zzyy: pointer to new music data
+
+	; update music id
+	ld hl, CHANNEL_MUSIC_ID
+	add hl, bc
+	ld a, [hli]
+	ld [wMusicID], a
+	ld a, [hl]
+	ld [wMusicID + 1], a
+	; update music bank
+	ld hl, CHANNEL_MUSIC_BANK
+	add hl, bc
+	ld a, [hl]
+	ld [wMusicBank], a
+	; get pointer to new channel header
+	call GetMusicByte
+	ld l, a
+	call GetMusicByte
+	ld h, a
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	push bc ; save current channel
+	call LoadChannel
+	call StartChannel
+	pop bc ; restore current channel
+	ret
+
+Music_NewSong:
+; new song
+; params: 2
+;	de: song id
+	call GetMusicByte
+	ld e, a
+	call GetMusicByte
+	ld d, a
+	push bc
+	call _PlayMusic
+	pop bc
+	ret
+
+GetMusicByte:
+; returns byte from current address in a
+; advances to next byte in music data
+; input: bc = start of current channel
+	push hl
+	push de
+	; load address into de
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld a, [hli]
+	ld e, a
+	ld d, [hl]
+	; load bank into a
+	ld hl, CHANNEL_MUSIC_BANK
+	add hl, bc
+	ld a, [hl]
+	; get byte
+	call _LoadMusicByte ; load data into wCurMusicByte
+	inc de ; advance to next byte for next time this is called
+	; update channeldata address
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	ld a, e
+	ld [hli], a
+	ld [hl], d
+	; cleanup
+	pop de
+	pop hl
+	; store channeldata in a
+	ld a, [wCurMusicByte]
+	ret
+
+GetFrequency:
+; generate frequency
+; input:
+; 	d: octave
+;	e: pitch
+; output:
+; 	de: frequency
+
+; get octave
+	; get starting octave
+	ld hl, CHANNEL_PITCH_OFFSET
+	add hl, bc
+	ld a, [hl]
+	swap a ; hi nybble
+	and $f
+	; add current octave
+	add d
+	push af ; we'll use this later
+	; get starting octave
+	ld hl, CHANNEL_PITCH_OFFSET
+	add hl, bc
+	ld a, [hl]
+	and $f ; lo nybble
+	ld l, a ; ok
+	ld d, 0
+	ld h, d
+	add hl, de ; add current pitch
+	add hl, hl ; skip 2 bytes for each
+	ld de, FrequencyTable
+	add hl, de
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; get our octave
+	pop af
+	; shift right by [7 - octave] bits
+.loop
+	; [7 - octave] loops
+	cp $7
+	jr nc, .ok
+	; sra de
+	sra d
+	rr e
+	inc a
+	jr .loop
+
+.ok
+	ld a, d
+	and $7 ; top 3 bits for frequency (11 total)
+	ld d, a
+	ret
+
+SetNoteDuration:
+; input: a = note duration in 16ths
+	; store delay units in de
+	inc a
+	ld e, a
+	ld d, 0
+	; store NoteLength in a
+	ld hl, CHANNEL_NOTE_LENGTH
+	add hl, bc
+	ld a, [hl]
+	; multiply NoteLength by delay units
+	ld l, 0 ; just multiply
+	call .Multiply
+	ld a, l ; low
+	; store Tempo in de
+	ld hl, CHANNEL_TEMPO
+	add hl, bc
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; add ???? to the next result
+	ld hl, CHANNEL_FIELD16
+	add hl, bc
+	ld l, [hl]
+	; multiply Tempo by last result (NoteLength * LOW(delay))
+	call .Multiply
+	; copy result to de
+	ld e, l
+	ld d, h
+	; store result in ????
+	ld hl, CHANNEL_FIELD16
+	add hl, bc
+	ld [hl], e
+	; store result in NoteDuration
+	ld hl, CHANNEL_NOTE_DURATION
+	add hl, bc
+	ld [hl], d
+	ret
+
+.Multiply:
+; multiplies a and de
+; adds the result to l
+; stores the result in hl
+	ld h, 0
+.loop
+	; halve a
+	srl a
+	; is there a remainder?
+	jr nc, .skip
+	; add it to the result
+	add hl, de
+.skip
+	; add de, de
+	sla e
+	rl d
+	; are we done?
+	and a
+	jr nz, .loop
+	ret
+
+SetGlobalTempo:
+	push bc ; save current channel
+	; are we dealing with music or sfx?
+	ld a, [wCurChannel]
+	cp CHAN5
+	jr nc, .sfxchannels
+	ld bc, wChannel1
+	call Tempo
+	ld bc, wChannel2
+	call Tempo
+	ld bc, wChannel3
+	call Tempo
+	ld bc, wChannel4
+	call Tempo
+	jr .end
+
+.sfxchannels
+	ld bc, wChannel5
+	call Tempo
+	ld bc, wChannel6
+	call Tempo
+	ld bc, wChannel7
+	call Tempo
+	ld bc, wChannel8
+	call Tempo
+.end
+	pop bc ; restore current channel
+	ret
+
+Tempo:
+; input:
+; 	de: note length
+	; update Tempo
+	ld hl, CHANNEL_TEMPO
+	add hl, bc
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	; clear ????
+	xor a
+	ld hl, CHANNEL_FIELD16
+	add hl, bc
+	ld [hl], a
+	ret
+
+StartChannel:
+	call SetLRTracks
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_CHANNEL_ON, [hl] ; turn channel on
+	ret
+
+SetLRTracks:
+; set tracks for a the current channel to default
+; seems to be redundant since this is overwritten by stereo data later
+	push de
+	; store current channel in de
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	ld e, a
+	ld d, 0
+	; get this channel's lr tracks
+	call GetLRTracks
+	add hl, de ; de = channel 0-3
+	ld a, [hl]
+	; load lr tracks into Tracks
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	ld [hl], a
+	pop de
+	ret
+
+_PlayMusic::
+; load music
+	call MusicOff
+	ld hl, wMusicID
+	ld [hl], e ; song number
+	inc hl
+	ld [hl], d ; (always 0)
+	ld hl, Music
+	add hl, de ; three
+	add hl, de ; byte
+	add hl, de ; pointer
+	ld a, [hli]
+	ld [wMusicBank], a
+	ld e, [hl]
+	inc hl
+	ld d, [hl] ; music header address
+	call LoadMusicByte ; store first byte of music header in a
+	rlca
+	rlca
+	maskbits NUM_MUSIC_CHANS
+	inc a
+.loop
+; start playing channels
+	push af
+	call LoadChannel
+	call StartChannel
+	pop af
+	dec a
+	jr nz, .loop
+	xor a
+	ld [wUnusedMusicF9Flag], a
+	ld [wChannel1JumpCondition], a
+	ld [wChannel2JumpCondition], a
+	ld [wChannel3JumpCondition], a
+	ld [wChannel4JumpCondition], a
+	ld [wNoiseSampleAddress], a
+	ld [wNoiseSampleAddress + 1], a
+	ld [wNoiseSampleDelay], a
+	ld [wMusicNoiseSampleSet], a
+	call MusicOn
+	ret
+
+_PlayCry::
+; Play cry de using parameters:
+;	wCryPitch
+;	wCryLength
+
+	call MusicOff
+
+; Overload the music id with the cry id
+	ld hl, wMusicID
+	ld [hl], e
+	inc hl
+	ld [hl], d
+
+; 3-byte pointers (bank, address)
+	ld hl, Cries
+	add hl, de
+	add hl, de
+	add hl, de
+
+	ld a, [hli]
+	ld [wMusicBank], a
+
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+
+; Read the cry's sound header
+	call LoadMusicByte
+	; Top 2 bits contain the number of channels
+	rlca
+	rlca
+	maskbits NUM_MUSIC_CHANS
+
+; For each channel:
+	inc a
+.loop
+	push af
+	call LoadChannel
+
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_REST, [hl]
+
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_CRY_PITCH, [hl]
+
+	ld hl, CHANNEL_CRY_PITCH
+	add hl, bc
+	ld a, [wCryPitch]
+	ld [hli], a
+	ld a, [wCryPitch + 1]
+	ld [hl], a
+
+; No tempo for channel 4
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	cp CHAN4
+	jr nc, .start
+
+; Tempo is effectively length
+	ld hl, CHANNEL_TEMPO
+	add hl, bc
+	ld a, [wCryLength]
+	ld [hli], a
+	ld a, [wCryLength + 1]
+	ld [hl], a
+.start
+	call StartChannel
+	ld a, [wStereoPanningMask]
+	and a
+	jr z, .next
+
+; Stereo only: Play cry from the monster's side.
+; This only applies in-battle.
+
+	ld a, [wOptions]
+	bit STEREO, a
+	jr z, .next
+
+; [Tracks] &= [wCryTracks]
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	ld a, [hl]
+	ld hl, wCryTracks
+	and [hl]
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	ld [hl], a
+
+.next
+	pop af
+	dec a
+	jr nz, .loop
+
+; Cries play at max volume, so we save the current volume for later.
+	ld a, [wLastVolume]
+	and a
+	jr nz, .end
+
+	ld a, [wVolume]
+	ld [wLastVolume], a
+	ld a, MAX_VOLUME
+	ld [wVolume], a
+
+.end
+	ld a, 1 ; stop playing music
+	ld [wSFXPriority], a
+	call MusicOn
+	ret
+
+_PlaySFX::
+; clear channels if they aren't already
+	call MusicOff
+	ld hl, wChannel5Flags1
+	bit SOUND_CHANNEL_ON, [hl] ; ch5 on?
+	jr z, .ch6
+	res SOUND_CHANNEL_ON, [hl] ; turn it off
+	xor a
+	ldh [rNR11], a ; length/wavepattern = 0
+	ld a, $8
+	ldh [rNR12], a ; envelope = 0
+	xor a
+	ldh [rNR13], a ; frequency lo = 0
+	ld a, $80
+	ldh [rNR14], a ; restart sound (freq hi = 0)
+	xor a
+	ld [wSoundInput], a ; global sound off
+	ldh [rNR10], a ; sweep = 0
+.ch6
+	ld hl, wChannel6Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr z, .ch7
+	res SOUND_CHANNEL_ON, [hl] ; turn it off
+	xor a
+	ldh [rNR21], a ; length/wavepattern = 0
+	ld a, $8
+	ldh [rNR22], a ; envelope = 0
+	xor a
+	ldh [rNR23], a ; frequency lo = 0
+	ld a, $80
+	ldh [rNR24], a ; restart sound (freq hi = 0)
+.ch7
+	ld hl, wChannel7Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr z, .ch8
+	res SOUND_CHANNEL_ON, [hl] ; turn it off
+	xor a
+	ldh [rNR30], a ; sound mode #3 off
+	ldh [rNR31], a ; length/wavepattern = 0
+	ld a, $8
+	ldh [rNR32], a ; envelope = 0
+	xor a
+	ldh [rNR33], a ; frequency lo = 0
+	ld a, $80
+	ldh [rNR34], a ; restart sound (freq hi = 0)
+.ch8
+	ld hl, wChannel8Flags1
+	bit SOUND_CHANNEL_ON, [hl]
+	jr z, .chscleared
+	res SOUND_CHANNEL_ON, [hl] ; turn it off
+	xor a
+	ldh [rNR41], a ; length/wavepattern = 0
+	ld a, $8
+	ldh [rNR42], a ; envelope = 0
+	xor a
+	ldh [rNR43], a ; frequency lo = 0
+	ld a, $80
+	ldh [rNR44], a ; restart sound (freq hi = 0)
+	xor a
+	ld [wNoiseSampleAddress], a
+	ld [wNoiseSampleAddress + 1], a
+.chscleared
+; start reading sfx header for # chs
+	ld hl, wMusicID
+	ld [hl], e
+	inc hl
+	ld [hl], d
+	ld hl, SFX
+	add hl, de ; three
+	add hl, de ; byte
+	add hl, de ; pointers
+	; get bank
+	ld a, [hli]
+	ld [wMusicBank], a
+	; get address
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	; get # channels
+	call LoadMusicByte
+	rlca ; top 2
+	rlca ; bits
+	maskbits NUM_MUSIC_CHANS
+	inc a ; # channels -> # loops
+.startchannels
+	push af
+	call LoadChannel ; bc = current channel
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_SFX, [hl]
+	call StartChannel
+	pop af
+	dec a
+	jr nz, .startchannels
+	call MusicOn
+	xor a
+	ld [wSFXPriority], a
+	ret
+
+PlayStereoSFX::
+; play sfx de
+
+	call MusicOff
+
+; standard procedure if stereo's off
+	ld a, [wOptions]
+	bit STEREO, a
+	jp z, _PlaySFX
+
+; else, let's go ahead with this
+	ld hl, wMusicID
+	ld [hl], e
+	inc hl
+	ld [hl], d
+
+; get sfx ptr
+	ld hl, SFX
+	add hl, de
+	add hl, de
+	add hl, de
+
+; bank
+	ld a, [hli]
+	ld [wMusicBank], a
+; address
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+
+; bit 2-3
+	call LoadMusicByte
+	rlca
+	rlca
+	maskbits NUM_MUSIC_CHANS
+	inc a
+
+.loop
+	push af
+	call LoadChannel
+
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_SFX, [hl]
+
+	push de
+	; get tracks for this channel
+	ld a, [wCurChannel]
+	maskbits NUM_MUSIC_CHANS
+	ld e, a
+	ld d, 0
+	call GetLRTracks
+	add hl, de
+	ld a, [hl]
+	ld hl, wStereoPanningMask
+	and [hl]
+
+	ld hl, CHANNEL_TRACKS
+	add hl, bc
+	ld [hl], a
+
+	ld hl, CHANNEL_FIELD30
+	add hl, bc
+	ld [hl], a
+
+	ld a, [wCryTracks]
+	cp 2 ; ch 1-2
+	jr c, .skip
+
+; ch3-4
+	ld a, [wSFXDuration]
+
+	ld hl, CHANNEL_FIELD2E
+	add hl, bc
+	ld [hl], a
+
+	ld hl, CHANNEL_FIELD2F
+	add hl, bc
+	ld [hl], a
+
+	ld hl, CHANNEL_FLAGS2
+	add hl, bc
+	set SOUND_UNKN_0F, [hl]
+
+.skip
+	pop de
+
+; turn channel on
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	set SOUND_CHANNEL_ON, [hl] ; on
+
+; done?
+	pop af
+	dec a
+	jr nz, .loop
+
+; we're done
+	call MusicOn
+	ret
+
+LoadChannel:
+; prep channel for use
+; input:
+; 	de:
+	; get pointer to current channel
+	call LoadMusicByte
+	inc de
+	and $7 ; bit 0-2 (current channel)
+	ld [wCurChannel], a
+	ld c, a
+	ld b, 0
+	ld hl, ChannelPointers
+	add hl, bc
+	add hl, bc
+	ld c, [hl]
+	inc hl
+	ld b, [hl] ; bc = channel pointer
+	ld hl, CHANNEL_FLAGS1
+	add hl, bc
+	res SOUND_CHANNEL_ON, [hl] ; channel off
+	call ChannelInit
+	; load music pointer
+	ld hl, CHANNEL_MUSIC_ADDRESS
+	add hl, bc
+	call LoadMusicByte
+	ld [hli], a
+	inc de
+	call LoadMusicByte
+	ld [hl], a
+	inc de
+	; load music id
+	ld hl, CHANNEL_MUSIC_ID
+	add hl, bc
+	ld a, [wMusicID]
+	ld [hli], a
+	ld a, [wMusicID + 1]
+	ld [hl], a
+	; load music bank
+	ld hl, CHANNEL_MUSIC_BANK
+	add hl, bc
+	ld a, [wMusicBank]
+	ld [hl], a
+	ret
+
+ChannelInit:
+; make sure channel is cleared
+; set default tempo and note length in case nothing is loaded
+; input:
+;   bc = channel struct pointer
+	push de
+	xor a
+	; get channel struct location and length
+	ld hl, CHANNEL_MUSIC_ID ; start
+	add hl, bc
+	ld e, CHANNEL_STRUCT_LENGTH ; channel struct length
+	; clear channel
+.loop
+	ld [hli], a
+	dec e
+	jr nz, .loop
+	; set tempo to default ($100)
+	ld hl, CHANNEL_TEMPO
+	add hl, bc
+	xor a
+	ld [hli], a
+	inc a
+	ld [hl], a
+	; set note length to default ($1) (fast)
+	ld hl, CHANNEL_NOTE_LENGTH
+	add hl, bc
+	ld [hl], a
+	pop de
+	ret
+
+LoadMusicByte::
+; input:
+;   de = current music address
+; output:
+;   a = wCurMusicByte
+	ld a, [wMusicBank]
+	call _LoadMusicByte
+	ld a, [wCurMusicByte]
+	ret
+
+INCLUDE "audio/notes.asm"
+
+INCLUDE "audio/wave_samples.asm"
+
+INCLUDE "audio/drumkits.asm"
+
+GetLRTracks:
+; gets the default sound l/r channels
+; stores mono/stereo table in hl
+	ld a, [wOptions]
+	bit STEREO, a
+	; made redundant, could have had a purpose in gold
+	jr nz, .stereo
+	ld hl, MonoTracks
+	ret
+
+.stereo
+	ld hl, StereoTracks
+	ret
+
+MonoTracks:
+; bit corresponds to track #
+; hi: left channel
+; lo: right channel
+	db $11, $22, $44, $88
+
+StereoTracks:
+; made redundant
+; seems to be modified on a per-song basis
+	db $11, $22, $44, $88
+
+ChannelPointers:
+; music channels
+	dw wChannel1
+	dw wChannel2
+	dw wChannel3
+	dw wChannel4
+; sfx channels
+	dw wChannel5
+	dw wChannel6
+	dw wChannel7
+	dw wChannel8
+
+ClearChannels::
+; runs ClearChannel for all 4 channels
+; doesn't seem to be used, but functionally identical to MapSetup_Sound_Off
+	ld hl, rNR50
+	xor a
+	ld [hli], a
+	ld [hli], a
+	ld a, $80
+	ld [hli], a
+	ld hl, rNR10
+	ld e, NUM_MUSIC_CHANS
+.loop
+	call ClearChannel
+	dec e
+	jr nz, .loop
+	ret
+
+ClearChannel:
+; input: hl = beginning hw sound register (rNR10, rNR20, rNR30, rNR40)
+; output: 00 00 80 00 80
+
+;   sound channel   1      2      3      4
+	xor a
+	ld [hli], a ; rNR10, rNR20, rNR30, rNR40 ; sweep = 0
+
+	ld [hli], a ; rNR11, rNR21, rNR31, rNR41 ; length/wavepattern = 0
+	ld a, $8
+	ld [hli], a ; rNR12, rNR22, rNR32, rNR42 ; envelope = 0
+	xor a
+	ld [hli], a ; rNR13, rNR23, rNR33, rNR43 ; frequency lo = 0
+	ld a, $80
+	ld [hli], a ; rNR14, rNR24, rNR34, rNR44 ; restart sound (freq hi = 0)
+	ret
+
+PlayTrainerEncounterMusic::
+; input: e = trainer type
+	; turn fade off
+	xor a
+	ld [wMusicFade], a
+	; play nothing for one frame
+	push de
+	ld de, MUSIC_NONE
+	call PlayMusic
+	call DelayFrame
+	; play new song
+	call MaxVolume
+	pop de
+	ld d, $00
+	ld hl, TrainerEncounterMusic
+	add hl, de
+	ld e, [hl]
+	call PlayMusic
+	ret