YM3812 or OPL2 is the “FM Operator type L (OPLII) synthesizer” used famously in the AdLib Music Synthesizer Card and Sound Blaster family of sound cards. It is a direct superset of (and shares a pin-out with) the YM3526 OPL chip, as used on the C64 FM sound expansion module. Its successor, the YMF262 or OPL3, supported 4-channel output and twice as many channels/operators and twice as many waveforms, as well as 4-op FM synthesis.

Official Documentation:

Datasheets

The YM3812/OPL2 datasheet can be found here.
The YM3526/OPL datasheet can be found here.

Known errata/omissions:

Omission: The /IRQ pin is open collector on both the YM3526/OPL and YM3812/OPL2.
Errata: The YM3526/OPL datasheet is missing the bar over the /RD and /WR signals in the truth table
Errata: Both the YM3526/OPL and YM3812/OPL2 datasheets list pin 1 on the diagram as VSS, it should be VCC. This is corrected in the YM3812/OPL2 application manual.
Errata: Bit D5(0x20) 'OPL2 MODE' of the test register(0x01) in the YM3812/OPL2 datasheet is improperly explained on both the datasheet and in the application manual, see below.

Application Manuals

The YM3526 application manual is not scanned. If you have a copy, please let us know!
The YM3812/OPL2 application manual can be found here.
The YMF262/OPL3 application manual can be found here.

Known errata/omissions:

Errata: Table 3-2 on page 12 of the YM3812/OPL2 application manual has the D4 value in the first column incorrect for the second entry from the top: the top entry is 0, and the second entry is listed as 0 but should be 1.
Errata: Bit D5(0x20) 'OPL2 MODE' of the test register(0x01) in the YM3812/OPL2 datasheet is improperly explained on both the datasheet and in the application manual. When bit D5 (0x20) is CLEAR, writes to registers 0xE0-0xF5 are suppressed, but the operation of said registers continues with whatever value was last written to them. This means if you set TEST(0x01) bit D5, write non-zero values to registers 0xE0-0xF5, then clear TEST(0x01) bit D5, the wave generators will continue to use the values previously written to 0xE0-0xF5 even though the chip is technically in 'non OPL2' mode. To work around this, before switching the chip to 'non OPL2' mode, ensure the chip is in 'OPL2' mode by writing 0x20 to TEST(0x01), then write values of 0x00 to all registers from 0xE0-0xF5, and finally write 0x00 to TEST(0x01).

Chip-specific Notes

YM2413/VRC7

OPL Light/Light, aka OPLL, is a cost-reduced version of OPL2 that hard-codes 15 preset instruments and allows for 1 custom instrument to be created. The instrument ROM saves silicon die space compared to registers. One nagging problem with OPLL is that up until recently, there was no known way to extract the instrument ROM contents. Thus, emulation of preset instruments was based on empirical approximations.

YM2413 D0/D1 debug state

from Nuke.YKT's notes at https://pastebin.com/H5s4WQQ8 :

YM2413 test data output format(!!not verified on hardware!!).
/CS = 0
/WE = 1
A0  = 0
D0 and D1 serially output test data with internal clock rate
Internal clock rate is MCLK/4
Clock 0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17
D0:   P8 P7 P6 P5 P4 P3 P2 P1 P0 E6 E5 E4 E2 E1 E0 0  0  0
D1:   C8 C7 C6 C5 C4 C3 C2 C1 C0 0  0  0  0  0  0  0  0  0
 
Px - Operator 0 phase generator output LSB bits
Ex - Operator 17 envelope generator output
Cx - Channel 6(?) output

YM2413 and VRC7 TEST register (0x0F)

TEST (0x0F)
	76543210
	|||||||\- if 1, Disables Car/Mod EG units, EG output is forced to 0 (max volume). This can be used as a crude DAC test, see below.
	||||||\-- if 1, resets (and holds, while active) the Trem and Vib LFO counts to 0, and resets the rhythm LFSR to all 1s.
	|||||\--- if 1, resets (and holds, while active) the PG count for Car/Mod at 0 (this effectively silences the chip)
	||||\---- if 1, the EG unit clock comes from VRC7 'D2' Pin, and the Trem and Vib LFO clock dividers are disabled, so they increment once per clock (x64 and x1024 their usual clock rates, respectively)
	|||\----- Does nothing?
	||\------ Does nothing?
	|\------- Does nothing?
	\-------- Does nothing?

If bit 0 is set, this can be combined with setting bit 2, and writing the 'desired DAC' (really, offset in the SINE ROM) value to register 0x10+n (or any of the other frequency registers). Bit 2 will reset the phase generator offset to 0 every tick, which combined with 0x10 to set the frequency LSB (which is added to the phase generator offset), can be used to crudely force the DAC to any specific value in the sine wave. Setting the frequency MSB (0x20+n) should also similarly affect this. The Volume and instrument settings in (0x30+n) still take effect, as do carrier/modulator effects, so keep this in mind.

VRC7 Debug Mode

TODO (see https://pastebin.com/2gAwGmFT )

<nukeykt> VRC7 D0-D7 are bidirectional. Internally data bus connected to 8-bit multiplexer and with right combination of chip's pins it's possible to configure it. Internal instrument bus connected to this multiplexer, so it's possible to dump it

<nukeykt> For all configs A13(pin 2)=1, M2(pin 47)=0, P15=0, […] For config 0: /CS=1, /WR=1, A0=1, for config 1: /CS=1, /WR=1, A0=0, etc.

YM2413 Instrument ROM

These values were initially created using hardware tests by nukeykt, but later were corrected by crosschecking data with the visible bits on the fhb013 (presumably ym2413b) die shot, located at https://siliconpr0n.org/archive/doku.php?id=digshadow:yamaha:fhb013 .

/* Order of array = { modulator, carrier } */
typedef struct {
    Bit8u tl;
    Bit8u dc;
    Bit8u dm;
    Bit8u fb;
    Bit8u am[2];
    Bit8u vib[2];
    Bit8u et[2];
    Bit8u ksr[2];
    Bit8u multi[2];
    Bit8u ksl[2];
    Bit8u ar[2];
    Bit8u dr[2];
    Bit8u sl[2];
    Bit8u rr[2];
} opll_patch_t;

static const opll_patch_t patch_ym2413[opll_patch_max] = {
    { 0x1e, 0x01, 0x00, 0x07,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x0d, 0x07 },{ 0x00, 0x08 },{ 0x00, 0x01 },{ 0x00, 0x07 } },
    { 0x1a, 0x00, 0x01, 0x05,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x03, 0x01 },{ 0x00, 0x00 },{ 0x0d, 0x0f },{ 0x08, 0x07 },{ 0x02, 0x01 },{ 0x03, 0x03 } },
    { 0x19, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x03, 0x01 },{ 0x02, 0x00 },{ 0x0f, 0x0c },{ 0x02, 0x04 },{ 0x01, 0x02 },{ 0x01, 0x03 } },
    { 0x0e, 0x00, 0x00, 0x07,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x06 },{ 0x08, 0x04 },{ 0x07, 0x02 },{ 0x00, 0x07 } },
    { 0x1e, 0x00, 0x00, 0x06,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x02, 0x01 },{ 0x00, 0x00 },{ 0x0e, 0x07 },{ 0x00, 0x06 },{ 0x00, 0x02 },{ 0x00, 0x08 } },
    { 0x16, 0x00, 0x00, 0x05,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x02 },{ 0x00, 0x00 },{ 0x0e, 0x07 },{ 0x00, 0x01 },{ 0x00, 0x01 },{ 0x00, 0x08 } },
    { 0x1d, 0x00, 0x00, 0x07,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x08, 0x08 },{ 0x02, 0x01 },{ 0x01, 0x00 },{ 0x00, 0x07 } },
    { 0x2d, 0x01, 0x00, 0x04,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x03, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x07 },{ 0x02, 0x02 },{ 0x00, 0x00 },{ 0x00, 0x07 } },
    { 0x1b, 0x00, 0x00, 0x06,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x06, 0x06 },{ 0x04, 0x05 },{ 0x01, 0x01 },{ 0x00, 0x07 } },
    { 0x0b, 0x01, 0x01, 0x00,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x08, 0x0f },{ 0x05, 0x07 },{ 0x07, 0x00 },{ 0x01, 0x07 } },
    { 0x03, 0x01, 0x00, 0x01,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x03, 0x01 },{ 0x02, 0x00 },{ 0x0f, 0x0e },{ 0x0a, 0x04 },{ 0x01, 0x00 },{ 0x00, 0x04 } },
    { 0x24, 0x00, 0x00, 0x07,{ 0x00, 0x01 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x07, 0x01 },{ 0x00, 0x00 },{ 0x0f, 0x0f },{ 0x08, 0x08 },{ 0x02, 0x01 },{ 0x02, 0x02 } },
    { 0x0c, 0x00, 0x00, 0x05,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x0c, 0x0f },{ 0x02, 0x05 },{ 0x02, 0x04 },{ 0x00, 0x02 } },
    { 0x15, 0x00, 0x00, 0x03,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x0c, 0x09 },{ 0x09, 0x05 },{ 0x00, 0x00 },{ 0x03, 0x02 } },
    { 0x09, 0x00, 0x00, 0x03,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x02, 0x00 },{ 0x0f, 0x0e },{ 0x01, 0x04 },{ 0x04, 0x01 },{ 0x00, 0x03 } },

    { 0x18, 0x00, 0x01, 0x07,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x0d, 0x00 },{ 0x0f, 0x00 },{ 0x06, 0x00 },{ 0x0a, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x0c, 0x00 },{ 0x08, 0x00 },{ 0x0a, 0x00 },{ 0x07, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x05, 0x00 },{ 0x00, 0x00 },{ 0x0f, 0x00 },{ 0x08, 0x00 },{ 0x05, 0x00 },{ 0x09, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0f },{ 0x00, 0x08 },{ 0x00, 0x06 },{ 0x00, 0x0d } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0d },{ 0x00, 0x08 },{ 0x00, 0x04 },{ 0x00, 0x08 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0a },{ 0x00, 0x0a },{ 0x00, 0x05 },{ 0x00, 0x05 } }
};

This translates into a patchset of:

0: user patch (irrelevant)
1: $71 $61 $1E $17 $D0 $78 $00 $17
2: $13 $41 $1A $0D $D8 $F7 $23 $13
3: $13 $01 $99 $00 $F2 $C4 $11 $23
4: $31 $61 $0E $07 $A8 $64 $70 $27
5: $32 $21 $1E $06 $E0 $76 $00 $28
6: $31 $22 $16 $05 $E0 $71 $00 $18
7: $21 $61 $1D $07 $82 $81 $10 $07
8: $23 $21 $2D $14 $A2 $72 $00 $07
9: $61 $61 $1B $06 $64 $65 $10 $17
A: $41 $61 $0B $18 $85 $F7 $71 $07
B: $13 $01 $83 $11 $FA $E4 $10 $04
C: $17 $C1 $24 $07 $F8 $F8 $22 $12
D: $61 $50 $0C $05 $C2 $F5 $20 $42
E: $01 $01 $55 $03 $C9 $95 $03 $02
F: $61 $41 $89 $03 $F1 $E4 $40 $13

Drums
BD   : $01 $01 $18 $0F $DF $F8 $6A $6D
SD/HH: $01 $01 $00 $00 $C8 $D8 $A7 $48
TM/TC: $05 $01 $00 $00 $F8 $AA $59 $55

VRC7 Instrument ROM Dump

Fellow Yamaha enthusiast NukeYKT dumped the instrument and rhythm tables using the aforementioned debug mode. The tables are reproduced here:

/* Order of array = { modulator, carrier } */
typedef struct {
    Bit8u tl;
    Bit8u dc;
    Bit8u dm;
    Bit8u fb;
    Bit8u am[2];
    Bit8u vib[2];
    Bit8u et[2];
    Bit8u ksr[2];
    Bit8u multi[2];
    Bit8u ksl[2];
    Bit8u ar[2];
    Bit8u dr[2];
    Bit8u sl[2];
    Bit8u rr[2];
} opll_patch_t;

static const opll_patch_t patch_ds1001[opll_patch_max] = {
    { 0x05, 0x00, 0x00, 0x06,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x03, 0x01 },{ 0x00, 0x00 },{ 0x0e, 0x08 },{ 0x08, 0x01 },{ 0x04, 0x02 },{ 0x02, 0x07 } },
    { 0x14, 0x00, 0x01, 0x05,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x03, 0x01 },{ 0x00, 0x00 },{ 0x0d, 0x0f },{ 0x08, 0x06 },{ 0x02, 0x01 },{ 0x03, 0x02 } },
    { 0x08, 0x00, 0x01, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x0f, 0x0b },{ 0x0a, 0x02 },{ 0x02, 0x01 },{ 0x00, 0x02 } },
    { 0x0c, 0x00, 0x00, 0x07,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x06 },{ 0x08, 0x04 },{ 0x06, 0x02 },{ 0x01, 0x07 } },
    { 0x1e, 0x00, 0x00, 0x06,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x02, 0x01 },{ 0x00, 0x00 },{ 0x0e, 0x07 },{ 0x01, 0x06 },{ 0x00, 0x02 },{ 0x01, 0x08 } },
    { 0x06, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x02, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x0e },{ 0x03, 0x02 },{ 0x0f, 0x0f },{ 0x04, 0x04 } },
    { 0x1d, 0x00, 0x00, 0x07,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x08, 0x08 },{ 0x02, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x07 } },
    { 0x22, 0x01, 0x00, 0x07,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x03, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x07 },{ 0x02, 0x02 },{ 0x00, 0x01 },{ 0x01, 0x07 } },
    { 0x25, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x01, 0x01 },{ 0x05, 0x01 },{ 0x00, 0x00 },{ 0x04, 0x07 },{ 0x00, 0x03 },{ 0x07, 0x00 },{ 0x02, 0x01 } },
    { 0x0f, 0x00, 0x01, 0x07,{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x01, 0x00 },{ 0x05, 0x01 },{ 0x00, 0x00 },{ 0x0a, 0x0a },{ 0x08, 0x05 },{ 0x05, 0x00 },{ 0x01, 0x02 } },
    { 0x24, 0x00, 0x00, 0x07,{ 0x00, 0x01 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x07, 0x01 },{ 0x00, 0x00 },{ 0x0f, 0x0f },{ 0x08, 0x08 },{ 0x02, 0x01 },{ 0x02, 0x02 } },
    { 0x11, 0x00, 0x00, 0x06,{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x00 },{ 0x01, 0x03 },{ 0x00, 0x00 },{ 0x06, 0x07 },{ 0x05, 0x04 },{ 0x01, 0x01 },{ 0x08, 0x06 } },
    { 0x13, 0x00, 0x00, 0x05,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x02 },{ 0x03, 0x00 },{ 0x0c, 0x09 },{ 0x09, 0x05 },{ 0x00, 0x00 },{ 0x03, 0x02 } },
    { 0x0c, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x01, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x00 },{ 0x01, 0x03 },{ 0x00, 0x00 },{ 0x09, 0x0c },{ 0x04, 0x00 },{ 0x03, 0x0f },{ 0x03, 0x06 } },
    { 0x0d, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x01, 0x01 },{ 0x00, 0x01 },{ 0x01, 0x02 },{ 0x00, 0x00 },{ 0x0c, 0x0d },{ 0x01, 0x05 },{ 0x05, 0x00 },{ 0x06, 0x06 } },
    /* Rhythm Patches: rows 1 and 4 are bass drum, 2 and 5 are Snare Drum & Hi-Hat, 3 and 6 are Tom and Top Cymbal */
    { 0x18, 0x00, 0x01, 0x07,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x0d, 0x00 },{ 0x0f, 0x00 },{ 0x06, 0x00 },{ 0x0a, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x01, 0x00 },{ 0x00, 0x00 },{ 0x0c, 0x00 },{ 0x08, 0x00 },{ 0x0a, 0x00 },{ 0x07, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x05, 0x00 },{ 0x00, 0x00 },{ 0x0f, 0x00 },{ 0x08, 0x00 },{ 0x05, 0x00 },{ 0x09, 0x00 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0f },{ 0x00, 0x08 },{ 0x00, 0x06 },{ 0x00, 0x0d } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0d },{ 0x00, 0x08 },{ 0x00, 0x06 },{ 0x00, 0x08 } },
    { 0x00, 0x00, 0x00, 0x00,{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x00 },{ 0x00, 0x01 },{ 0x00, 0x00 },{ 0x00, 0x0a },{ 0x00, 0x0a },{ 0x00, 0x05 },{ 0x00, 0x05 } }
};

This translates into a patchset of:

0: user patch (irrelevant)
1: $03 $21 $05 $06 $E8 $81 $42 $27
2: $13 $41 $14 $0D $D8 $F6 $23 $12
3: $11 $11 $08 $08 $FA $B2 $20 $12
4: $31 $61 $0C $07 $A8 $64 $61 $27
5: $32 $21 $1E $06 $E1 $76 $01 $28
6: $02 $01 $06 $00 $A3 $E2 $F4 $F4
7: $21 $61 $1D $07 $82 $81 $11 $07
8: $23 $21 $22 $17 $A2 $72 $01 $17
9: $35 $11 $25 $00 $40 $73 $72 $01
A: $B5 $01 $0F $0F $A8 $A5 $51 $02
B: $17 $C1 $24 $07 $F8 $F8 $22 $12
C: $71 $23 $11 $06 $65 $74 $18 $16
D: $01 $02 $D3 $05 $C9 $95 $03 $02
E: $61 $63 $0C $00 $94 $C0 $33 $F6
F: $21 $72 $0D $00 $C1 $D5 $56 $06

Drums (silent due to no RO output pin(?) on VRC7, but present internally; these are likely shared with YM2413)
BD   : $01 $01 $18 $0F $DF $F8 $6A $6D
SD/HH: $01 $01 $00 $00 $C8 $D8 $A7 $68
TM/TC: $05 $01 $00 $00 $F8 $AA $59 $55

OPLL/VRC7 Patch Format

byte 0:
	76543210
	||||\\\\- MULT (Mod)
	|||\----- Key Scale Rate enable (Mod)
	||\------ Env Gen Type (0 = percussion/auto-key-off, 1 = sustain/normal) (Mod)
	|\------- Vibrato enable (Mod)
	\-------- Tremolo enable (Mod)

byte 1:
	76543210
	||||\\\\- MULT (Car)
	|||\----- Key Scale Rate enable (Car)
	||\------ Env Gen Type (0 = percussion/auto-key-off, 1 = sustain/normal) (Car)
	|\------- Vibrato enable (Car)
	\-------- Tremolo enable (Car)

byte 2:
	76543210
	||\\\\\\- Total Level, inverted (Mod)
	\\------- Key Scale Level (Mod)

byte 3:
	76543210
	|||||\\\- Feedback level (Mod)
	||||\---- WF select (sine vs halfsine, Mod)
	|||\----- WF select (sine vs halfsine, Car)
	||\------ Unused
	\\------- Key Scale Level (Car)

byte 4:
	76543210
	||||\\\\- Decay Rate, inverted (Mod)
	\\\\----- Attack Rate, inverted (Mod)

byte 5:
	76543210
	||||\\\\- Decay Rate, inverted (Car)
	\\\\----- Attack Rate, inverted (Car)

byte 6:
	76543210
	||||\\\\- Release Rate, inverted (Mod)
	\\\\----- Sustain Level, inverted (Mod)

byte 7:
	76543210
	||||\\\\- Release Rate, inverted (Car)
	\\\\----- Sustain Level, inverted (Car)

Table of Contents

Official Documentation:

Datasheets

Known errata/omissions:

Application Manuals

Known errata/omissions:

Chip-specific Notes

YM2413/VRC7

YM2413 D0/D1 debug state

YM2413 and VRC7 TEST register (0x0F)

VRC7 Debug Mode

YM2413 Instrument ROM

VRC7 Instrument ROM Dump

OPLL/VRC7 Patch Format

Table of Contents