GYB Version 1/2
===============

Header
------
Pos	Len	Description
--------------------------------
00	02	Signature: 26 12 (both decimal)
02	01	Version
03	01	Instrument Count: Melody Bank
04	01	Instrument Count: Drum Bank
05	100	Instrument Map (Melody
		-> FM instrument IDs for GM instruments/drums
		-> Melody/Drum Bank interleaved (melody 0, drum 0, melody 1, drum 1, ...)
105	01	[GYB v2 only] default LFO Speed
??	??	Instrument Data [Melody Bank]
??	??	Instrument Data [Drum Bank]
??	??	Instrument Names [Melody Bank]
??	??	Instrument Names [Drum Bank]
??	04	Checksum (calculated over whole file minus the checksum itself)
EOF

Instrument Data [v1]
---------------
00	1D	YM2612 Registers
		Order:	30 34 38 3C 40 44 48 4C
			50 54 58 5C 60 64 68 6C
			70 74 78 7C 80 84 88 8C
			90 94 98 9C B0
1D	01	Instrument Transposition (signed 8-bit)
		Drum Bank: default drum note (unsigned 8-bit)

Instrument Data [v2]
---------------
00	1E	YM2612 Registers
		Order:	30 34 38 3C 40 44 48 4C
			50 54 58 5C 60 64 68 6C
			70 74 78 7C 80 84 88 8C
			90 94 98 9C B0 B4
1E	01	Instrument Transposition (same as v1)
1F	01	Padding (set to 0)

Instrument Name
---------------
00	01	String Length n
01	n	String



GYB Version 3
=============

Header
------
Pos	Len	Description
--------------------------------
00	02	Signature: 26 12 (both decimal)
02	01	Version
03	01	default LFO Speed
04	04	File Size
08	04	File Offset: Instrument Banks
0C	04	File Offset: Instrument Maps


Instrument Bank
---------------
00	02	Instrument Count
02	??	Instrument Data

Instrument Data
---------------
00	02	Bytes used by this instrument (includes this value)
02	1E	YM2612 Registers
		Order:	30 34 38 3C 40 44 48 4C
			50 54 58 5C 60 64 68 6C
			70 74 78 7C 80 84 88 8C
			90 94 98 9C B0 B4
20	01	Instrument Transposition (signed 8-bit)
		Drum Bank: default drum note (unsigned 8-bit)
21	01	Bitfield: Additional Data
		Bit 0: Chord notes (additional notes that sound by playing this instrument)
22	??	additional data
??	01	String Length n
??	n	String


Chord notes
-----------
00	01	Number of Notes n
01	01*n	Notes (8-bit signed, relative to initial note)



Instrument Maps
---------------
00	??	Instrument Map: Melody [GM instrument -> FM instrument]
??	??	Instrument Map: Drum [GM drum kit sound -> FM instrument]

Instrument Map
--------------
00	??*80	128 (dec) Map Entries
		[Melody] each entry corresponds to one GM instrument
		[Drum] each entry corresponds to one GM instrument

Instrument Map Entry
--------------------
00	02	Map Sub-Entry Count n
02	04*n	Map Sub-Entries

00	01	Bank MSB (00 = default, FF = all) [Melody] / Drum Kit [Drum]
01	01	Bank LSB (FF = all) [Melody] / unused [Drum]
02	02	FM Instrument (Bit 15 = Drum Bank)