[Terms in general]
Flutter -> VolEnv/Volume Envelope
Note Fill -> Note Timeout (or maybe Note Stop)
Tempo Divider -> Tick Multiplier

[Functions]
S1 Git			S2 Git			S3K Git			new name	comments
Sound_Play		zCycleQueue		zCycleSoundQueue	DoSoundQueue	CycleSoundQueue doesn't sound bad either
Sound_ChkValue		zPlaySoundByIndex	zPlaySoundByIndex	PlaySoundID
TempoWait		TempoWait		TempoWait				S2/S3K don't *always* wait.
UpdateDAC		zDACUpdateTrack		zUpdateDACTrack				Those UpdateTrack routines could use standardized names.
						zUpdateFMorPSGTrack	UpdateTrack	They don't follow any pattern at all currently.
FMUpdateTrack		zFMUpdateTrack		
PSGUpdateTrack		zPSGUpdateTrack		zUpdatePSGTrack
FMDoNext/PSGDoNext	zFMDoNext/zPSGDoNext	zGetNextNote		ProcessTrack	or ProcessTrackData or something similar

Sound_PlayBGM		zPlayMusic		zPlayMusic
Sound_PlaySFX		zPlaySound_CheckRing	zPlaySound_CheckRing
Sound_PlaySpecial	
Sound_E0toE4		[no label]		[no label]
FadeOutMusic		zFadeOutMusic		zFadeOutMusic
StopSoundAndMusic	zStopSoundAndMusic	zMusicFade		StopAllSound
PlaySega		zPlaySegaSound		zPlaySegaSound

cfPreventAttack		cfPreventAttack		cfPreventAttack		HoldNote	"prevent attack" sounds too technical
						cfChangeVolume2		ChangeFMVolume2
cfChangePSGVolume	cfChangeFMVolume	cfChangeVolume		ChangeFMVolume
cfSetTempoDivider	cfSetTempoDivider				SetTickMult
cfSetTempoMod		cfSetTempoMod		cfSetTempoDivider	SetTickMultAll
						cfAlterModulation	SetModEnvFMPSG	"FMPSG" because separate envelope for FM and PSG channels.
						cfSetModulation		SetModEnvelope
						cfToggleAltFreqMode	RawFreqMode	"raw frequency" instead of "alternate"
						cfHaltSound		MusicPause	It explicitly pauses/resumes music tracks while SFX continue to play.
FlutterDone		zloc_522		zDoVolEnvRest		VolEnvHold	because it holds the envelope at the current level
						zDoVolEnvFullRest	VolEnvStop	because it stops the note (by setting volume to 0)

[Variables 1]
zTrackTempoDivider	zTrack.TempoDivider	zTrack.TempoDivider	TickMultiplier	or short "TickMult"
zTrackNoteFill		zTrack.NoteFill		zTrack.NoteFill		NoteTimeout	or "NoteStop" - "fill" is very misleading here
FM_Notes		zFrequencies		zFMFrequencies		FMFrequencies	standardize name
PSGFrequencies		zPSGFrequencies		zPSGFrequencies		
zTrackVolFlutter	zTrack.VolFlutter	zTrack.VolEnv		VolEnvIdx	The "instrument" is the actual envelope, this is the array index within the envelope.
zTrackVoiceIndex	VoiceIndex		VoiceIndex		Instrument	I prefer the term "instrument" instead of "voice" here.
						ModulationCtrl		ModEnv		for standardization with VolEnv

[Variables 2]
f_stopmusic		StopMusic		zPauseFlag		PauseMusic	It is used for pause/unpause only.
v_playsnd0		QueueToPlay		zNextSound		SoundID		Sound ID that is played.
v_playsnd1		SFXToPlay		zMusicNumber		SoundQueue0	The sound queue is processed and 1 ID is moved to the SoundID slot.
v_playsnd2		SFXStereoToPlay		zSFXNumber0		SoundQueue1
v_playnull		SFXUnknown		zSFXNumber1		SoundQueue2
f_voice_selector	zDoSFXFlag		zUpdatingSFX		??		I called it "Music Mode".