SEQUENCER TRACK DATA DEFINITION

track data blocks are prefixed with a timing value "delta"
it is the number of ticks to pass until processing the block

delta is a variable-width value [p]

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COMMANDS
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	opcode format: "2bit:upper, 6bit:lower"

	cmdbyte:name brief
		description
		[x] params
		[x] params...
		notes

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	00h:STOP end of track
		this implies 1F command too (end of block)

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	SOURCE
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	many source specifications.....

	01:SRCPSG0
	41:SRCPSG1
	81:SRCPSG2
	C1:SRCPSG3
		set source to PSG square duty 0->3

	02:SRCPSG4
	42:SRCPSG5
	82:SRCPSG6
	C2:SRCPSG7
		set source to PSG square duty 4->7

	03:SRCPCM8
	43:SRCPCM16
		set source to one-shot PCM
		[32] source address
		[16] source length (words)

	83:SRCLPCM8
	C3:SRCLPCM16
		set source to looped PCM
		[32] source address
		[16] source length (words)
		[16] source loop point (words)

	04:SRCADPCM
		set source to one-shot ADPCM
		[32] source address
		[16] source loop point (words)

	84:SRCLADPCM
		set source to looped ADPCM
		[32] source address
		[16] source loop length (words)
		[16] source loop point (words)

	05:SRCNOISE
		set source to PSG noise

	06:SRCTABLE
		set source from source table
		[p] direct source table index

	86:SRCITABLE
		set source from source table - indirect
		[p] indirect source table index

	07:reserved
	
	all SOURCE commands will perform KEY-ON
	
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	VOLUME/PANNING/PITCH
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	08:VOLUME
		set volume level
		[16] 16-bit volume level

	09:PAN
		set panning level
		[8] 7-bit panning level
	49:CPAN center panning level
	89:LPAN hard-left panning level
	C9:RPAN hard-right panning level
	
	0A:PERIOD set period
		[16] 16-bit period
	
	4A:APERIOD
		adjust period
		[8] signed 8-bit offset

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	VOLUME ENVELOPE
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	0B:ENVELOPE
		[8] config flags
			&1 = AR follows
			&2 = DR follows
			&4 = SL follows
			&8 = SR follows
			&16= RR follows
		
		(if corresponding bits are set:)
		[p] AR attack rate
		[p] DR decay rate
		[p] SL sustain level
		[p] SR sustain decay rate
		[p] RR release rate
		
		rates are specified in number of ticks that it will
		take to slide from 0->1 (ar) or 1->0 (dr,sr,rr)
		sustain level is 0.14 fixed point (0=0,16383=~1.0)
	8B:BYPASSENV
		bypass envelope
		bypass is set as default

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	KEY ON/OFF
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	0C:KEYON
		start new note
	8C:KEYOFF
		release current note

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	CUT
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	0D:CUT cut current note
		current note will be released and cut

	4D:CUTPREV
		released notes associated with channel will be cut

	8D:CUTALL
		all notes associated with channel will be released and cut

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	OTHER
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	0E:AUTORELEASE_ON
	8E:AUTORELEASE_OFF
		auto release: new notes will apply key-off to current

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	CONTROL
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	10:CHSEL select channel
		[8] sequencer channel selection (0-39)
		re-mapping is applied to tracks

	11:MVOL set track master volume
		[p] master volume scale: 0-16383 (Q14)

	12:TEMPO set track tempo
		[p] track tempo: x.24 fixed point ratio to 256hz internal cycle
		(ie "3932160" is 60hz (60/256*2^24))

	13:CUE track cue
		[8] user parameter

	14:AUTORELEASE_ALL
	94:AUTORELEASE_ALLOFF
		enable/disable auto release for all channels

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	1F:END end of block
		data is processed and next delta value follows
------------------------------------------------------------
	20-37: 24 custom channel slots
	38-3F: 8 custom global slots

 *** released notes
	notes that are keyed off will be able to be overwritten
	by new notes

voices:
0-15: hardware channels
16-31: software channels

special hardware use:
1,3 used for reverb (left,right)
4,5 used for audio stream
6,7 used for software mixing stream (30ch max)
8-13 psg square capable
14,15 psg noise capable

*****************************************************************
DATA TYPES
[8] 8-bit value
[16] 16-bit value
[24] 24-bit value
[32] 32-bit value
[p] variable length value
	7-bit data with 1-bit extend param
	if bit7 is set then another byte follows and extends the
	higher bit region, maximum length is 29 bits of data (7+7+7+8bits)