Mother Music Format.txt

MOTHER MUSIC FORMAT
v1.0

By Justin Olbrantz (Quantam)

The permanent home of this specification and others, with the latest updates, is https://github.com/TheRealQuantam/RetroDocs.

The Mother sound engine is the final version of the Hirokazu Tanaka engine which was derived from the Yukio Kaneoka engine dating all the way back to Nintendo's earliest NES games by Research and Development 1. An earlier version of the Tanaka engine would be used for the well-known Metroid and Kid Icarus, and the Mother engine would take Tanaka and R&D1 through the end of the NES era. Apart from Mother, other hit games to use the Mother engine include Dr. Mario and the legendary Tetris.

The Tanaka-Kaneoka engines show a clear progression of features culminating in the Mother engine. Most of the awful inflexibility of the Metroid engine previously documented is gone, with new music data-based mechanisms for timbre, tempo, and looping control. The engine appears to take some inspiration from the R&D4 engines such as that of Super Mario Bros. 3, adopting a per-channel version of their block/playlist structure. While the Metroid engine was decidedly a hybrid system, mixing music data with hard-coding, only 1 (new) part of the Mother engine is a hybrid: the pitch envelope system. Overall the engine is vastly more flexible than the Metroid engine and highly efficient at eliminating redundancy in music data, but the block system makes the engine vastly more complicated to compose for.

Basic Features:
- Single byte notes and rests, though current note length must be previously defined with an additional byte
+ Hybrid tempo system that mimics staff notation divisive rhythm
	- 5-octave chromatic scale from A1 (55 Hz) to E7 (2637 Hz) for square wave (game-specific); triangle is 1 octave lower.
	- 9 note lengths from whole notes through 16th notes with dots and triplets for some lengths for all tempos, plus several tempo-specific lengths (game-specific)
	- 8 tempos from 82 to 225 BPM (game-specific)
- 5 channels - square 1, square 2, triangle, noise, DMC - with 4 separate event sequences (DMC events are encoded on the noise channel)
+ Multi-timbre support
	- Square channels: duty cycle, channel volume or non-looping volume envelopes, looping pitch envelopes
	- Triangle channel: looping pitch envelopes
	- Global set of 10 noise presets (game-specific)
	- Global set of 2 DMC presets (game-specific)
- Single-level unnested loops
- Per-channel block structure allow reuse of data as well as more than 256 bytes per channel
- Global transpose setting

Major Differences with the Metroid Engine:
- Timbre, global tempo, and triangle auto-release now controllable by music data
- Support for DMC sounds
- New volume envelope format that is half the size but doesn't allow modification of duty cycle
- Pitch envelopes
- Global transpose setting settable by music data
- Track looping is now per-channel and no longer limited to whole track looping
- Per-channel block structure allows reuse of data as well as more than 256 bytes per channel

Some general notes in interpreting this specification:
- All word (16-bit) values in the format are little-endian, with the least-significant byte preceding the most-significant, unless noted otherwise.
- All values are unsigned unless noted otherwise.
- All numbers preceded by $ are hex, and in general unless they represent byte strings or addresses most numbers without $ are in decimal.
- Byte values are generally shown as hex "ab" where "a" is the high nibble and "b" is the low nibble (standard mathematical digit ordering). However, when it is necessary to show bit fields, bytes are shown in binary as "abcd efgh" (mathematical order); in bit fields "-" means that the value of the bit does not matter in the given context.
- Many command lists (e.g. channel data commands) are encoded ambiguously, where 1 value could be interpreted as multiple different commands (e.g. 00 could match 0n). These lists are ordered such that the first matching command is the correct interpretation.

Track Structure

At the highest level Mother's track structure is almost identical to Metroid's: a table of offsets into blocks containing the headers for each track; however, the headers contain less metadata and the metadata they do contain (such as tempo and transpose) are now merely the initial values, and may be changed by music data during play. However, due to the amount of music in an RPG like Mother and the self-imposed limitation of 256 byte-large blocks containing track headers, Mother has 2 banks of music, 1 for "low" tracks 1-$18 and the other for "high" tracks $19-$31; it is worth noting that these banks are nearly packed to the gills, with the maximum of $19 tracks per bank being possible with the 256-byte limit.

What is VERY different, however, is what the header's channel data addresses point to. Rather than pointing to the actual music data as in Metroid, they point to a playlist of blocks for the channel. This is an array of 16-bit words that specify the addresses of blocks of music data and in which order they should be played, terminated either by an end of track code or a goto code that specifies the channel should continue from a specified location in the playlist. The playlist performs the function of (infinitely) looping the track (though note that some tracks loop on some channels but eventually end the track on another), reusing blocks of music data like "subroutines" in other engines, and freeing the engine from the Metroid engine's limitation of 256-byte channel data (now each block is limited to 256 bytes); they may even be used for example to have square 1 and square 2 play the same sequence of notes with a delay on 1 channel or different timbre by having different first blocks that then both jump to the same playlist location. And while it is not recommendable to perform local loops with the playlist as channel music data loops are more efficient for that purpose, the playlist may be used to add additional levels of looping to a track.

Accordingly, the "end of track" 0 command in music data now means "end of block", and the "end of track" command is performed by the playlist. This means that most blocks on all channels will be terminated, however it is still possible for the final blocks of some channels to be unterminated because another channel will end the track before erroneous data is played.

Bank configuration:
$8000-$9fff: Bank $1c
$a000-$bfff: Bank $1d

1c:903e byte[$18]: Low track header offset table
1c:9056 byte[$19]: High track header offset table
1c:906f struct[$18]: Low track header block
1c:915f struct[$19]: High track header block

Track Header Format:
	+0 byte: Initial global transpose in modified sign-magnitude format with the format nmmm mmmm. If n is clear the transpose value = +m; if n is set the transpose value = -1 - m. The transpose value must be an even number, as it is 2x the number of semitones and fractional semitones are not supported.
	+1 byte: Initial note length table offset (implicitly, tempo). See Time and Tempo for a list of possible values.
	+2 word[4]: Channel playlist addresses in order of square 1, square 2, triangle, and noise, or a high byte of $ff (canonically $ffff) if none.
	
Example

81 0C 8F 99 97 99 9F 99 A7 99
81: Initial global transpose
	n = 1: Negative
	m = 1: With n = 1 the transpose value = -1 - 1 = -2 (-1 semitone)
0C: Initial note length table offset
	t = $c: Table offset $c: 180 BPM
8F 99: Square 1 channel playlist address $998f
97 99: Square 2 channel playlist address $9997
9F 99: Triangle 1 channel playlist address $999f
A7 99: Noise channel playlist address $99a7

Block Playlist Format (word values, shown in mathematical order, not their physical little-endian byte order):
00--: Global end of track. All channels stop when this is encountered on any channel.
ff-- AAAA: Goto. Set the current playlist location address (not block address) to A.
AAAA: Play the block of music data at address A.

Examples

Square 1 channel: 62 99 00 00
62 99: Play block address $9962
00 00: End of track

Square 2 channel of SAME track: 71 99
71 99: Play block address $9971

Note that there is NO termination for this channel, as the track will be terminated by the end of track command on square 1.

Square 1 playlist at $b0f8: 0C B1 15 B1 FF FF 02 B1
0C B1: Play block address $b10c
15 B1: Play block address $b115
FF FF 02 B1: Go to playlist address $b102

Square 2 playlist at $b100 of same track: 12 B1 1F B1 FF FF 02 B1
12 B1: Play block address $b112
1F B1: Play block address $b11f
FF FF 02 B1: Go to playlist address $b102. This looks familiar.

Triangle playlist of same track: 2F B1 00 00
2F B1: Play block address $b12f
00 00: End of track

Note 2 things here. $b102 is the second entry in the square 2 playlist (block $b11f); in other words, the square channels have a couple initial unique blocks before merging to the same data (square 1 is delayed by 26 frames, among other things). Second, triangle block $b12f is much longer than any of the square channel blocks (16 seconds per loop), so the square channels loop repeatedly until the triangle channel terminates the track at 8:33. The irony of this is that in fact the triangle channel IS looping (32 loops of 16 sec), but it's looping using the music data loop construct within the block; it is not at all clear why it was not simply made to loop infinitely like the rest.

Time and Tempo

The note length system in Mother is identical to that in Metroid, save that music data may change the table offset during play. Note/rest durations are frame-based, and a master table specifies note durations in frames. At any given point the track has a $10-element window into this table for use by all channels, and set note length commands select 1 of these lengths. This table is arranged (and used in game music) to provide 8 different tempos with a common set of 9 musical lengths with common indices; various other lengths are available based on the window used for the track, but they are not common between tempos.

The master table giving lengths in frames is:
0 :   4   8  16  32  64  24  48  12  10   5   2   1   5  10  20  40
10:  80  30  60  15  12   6   3   2   6  12  24  48  96  36  72  18
20:  16   8   3   1   4   2   0 144   7  14  28  56 112  42  84  21
30:  18   9   3   1   2   8  16  32  64 128  48  96  24  21  10   4
40:   1   2 192   9  18  36  72 144  54 108  27  24  10  20  40  80
50: 160  60 120  30  26  13   5   1   2  23  11  22  44  88 176  66
60: 132  33  29  14   5   1   2  23

When arranged by the base offsets used by the game the table looks like this:

          0   1   2   3    4   5    6   7   8    9   a  b  c  d  e    f
    BPM  16   8   4   2    1  4D   2D  8D  4T   8T  32
0  (225): 4   8  16  32   64  24   48  12  10*   5*  2  1
c  (180): 5  10  20  40   80  30   60  15  12*   6*  3* 2
18 (150): 6  12  24  48   96  36   72  18  16    8   3  1  4  2  0  144
28 (129): 7  14  28  56  112  42   84  21  18*   9*  3* 1  2
35 (113): 8  16  32  64  128  48   96  24  21*  10*  4  1  2  192
43 (100): 9  18  36  72  144  54  108  27  24     *   *
4c (90): 10  20  40  80  160  60  120  30  26*  13*  5  1  2  23
5a (82): 11  22  44  88  176  66  132  33  29*  14*  5* 1  2  23

Using these windows, the following standard length codes are defined:

          Whole  Half   4th   8th  16th  32nd
Normal:       4    3      2     1     0     a*
Dotted:            6      5     7
Triplet:                  8*    9*

* Triplets and 32nds in some tempos are not whole numbers of frames, and will not properly mix with other lengths. These can either be avoided in those tempos or worked around by varying the lengths of notes of that type by 1 frame or inserting short (e.g. 1 frame) rests so that 3 triplets or 2 32nds add up to the correct whole number of frames. Note critically that all lengths beyond quarter triplet are MISSING for 100 BPM.

Notes on the triangle wave channel are capable of auto-release prior to the end of the specified note duration. Depending on the current auto-release settings specified by the set timbre command on the triangle channel, notes may be set to either never auto-release, auto-release after a fixed number of frames (up to 8), or dynamic auto-release of notes 1 frame before the end of the note or after 15 frames, whichever is sooner.

Notes and Rests

The Mother engine uses 3 different key sets: 1 for melodic channels (though note that triangle is 1 octave lower than square channels) and 2 for the noise channel (1 for noise presets and 1 for DMC presets).

1 oddity of the Tanaka-Kaneoka engines is that rather than keys being numbered sequentially, key values for everything except DMC presets are actually byte offsets into various lookup tables (this made somewhat more sense for the Kaneoka engine and Kondo engine derived from it). For melodic keys that table is the pitch period table which has word-sized elements, resulting in all valid key values being even. For these keys it's easiest to pretend that the bottom bit is not part of the key value and must simply be 0, but the transpose feature added in the Mother engine exposes this detail as the transpose value is added directly to the key value to get the byte offset into the array. While not at all recommendable, it's possible to have both key values and transpose values be odd to produce an even sum that will correctly reference a key pitch. For this document we will pretend that melodic key numbers exclude the bottom bit, though there is 1 place where the truth of the matter can't be hidden.

The melodic key set has a nominal base key of A#1 for all known games, though for unknown and possibly historical reasons its key 0 is A1 and key 1 is rest. While the engine is capable of using key numbers 2-$4d and $50-$57 (additional ranges with an exploit), no known game uses the entire available range.

Mother's Key Table:

Oct  C  C#   D  D#   E   F  F#   G  G#   A  A#   B  Max Detune at B
1:                                       0*         0.96 cents
2:   2   3   4   5   6   7   8   9   a   b   c   d  1.91 cents
3:   e   f  10  11  12  13  14  15  16  17  18  19  3.83 cents
4:  1a  1b  1c  1d  1e  1f  20  21  22  23  24  25  7.69 cents
5:  26  27  28  29  2a  2b  2c  2d  2e  2f  30  31  15.49 cents
6:  32  33  34  35  36  37  38  39  3a  3b  3c  3d  31.41 cents
7:  3e  3f  40  41  42

* Key code 0 is an exploit: if key code 0 IMMEDIATELY follows a set length command it will be assumed to be a note/rest rather than being interpreted as an end of block command. While not relevant to any known game, this same exploit can be used with keys $4e-$4f and above $57.

Like the true way melodic keys work, noise codes are indices into an array of noise presets, though here they are 1-based offsets into entries of 3 bytes. Rest is code 1, and some games like Mother exploit the fact that only the first byte of the 3 is necessary to silence the channel to place the first preset at 2. All together, Mother supports the following presets: 2, 4, 7, $a, $d, $10, $13, $16, $19, $1c.

Finally there are the DMC presets. Each byte-sized key/rest command on the noise channel is actually 2 commands in 1: the low bits contain a noise preset code and the high bits contain a DMC preset code. There are actually 2 variants of the Mother engine, depending on whether 2 bits or 3 are dedicated to the DMC code. Mother uses 2 bits and is limited to 3 DMC presets, although it only uses 2. In both versions of the engine DMC key code 0, as well as any other unused codes, is rest for the DMC channel.

DMC Presets:
1: Kick/bass drum
2: Snare drum

Channel Data

1 major difference between the Tanaka-Kaneoka engines and non-Nintendo engines is that while each channel has separate music data, the end of track command (part of the playlist, in the Mother engine) applies globally, and all channels are affected when ANY channel encounters it. Because of this, it is not necessary to explicitly terminate all channels for tracks that do not loop, only the 1 that will reach its end first. Unlike the Metroid engine, however, all channels must be made to loop for looping tracks.

Channel Data Format:
00: End of block. Advance to the next entry in the channel's playlist.
9c nmmm mmmm: Set global transpose. If n is clear the transpose value = +m; if n is set the transpose value = -1 - m. The transpose value must be an even number, as it is 2x the number of semitones and fractional semitones are not supported.
9e tt: Set global note length table offset (implicitly, tempo) to t
ff: End loop. If loop counter is not 0 decrement and loop, else continue. MUST be in the same block as its start loop command.
bL: Set current channel note length code to L. For triangle set linear counter according to current triangle auto-release settings. Must be IMMEDIATELY followed by a note/rest.
cL (11nn nnnn): Begin loop and set number of times to play loop to n (1-$3e or 0 is interpreted as $100)

Melodic Channels Only:
9f pppx xxxx CC: Set channel timbre. MUST NOT be used on noise channel. Set pitch envelope to p (0 if none) and base ctrl 1 value to C.
	For square channels: Set volume envelope to x (0 if none), and C has the form ddLV vvvv:
		d: Duty cycle: 12.5% (0), 25% (1), 50% (2), or 75% (3)
		L: Disable length counter and play forever. Should always be set, as the engine does not provide any control over the length counter.
		V: If set v is the channel volume, else v is the volume decay speed. Should always be set.
		v: Channel volume 0-$f.
	For triangle channel: p (in addition to setting the pitch envelope), x, and C control auto-release in a way that seems contradictory and will be clarified later in this section. C has the form Fnnn nnnn:
		F: If set disables auto-release if n is non-0. If clear, apply n.
		n: The number of quarter-frames to play notes before auto-release.
	p and x set the auto-release settings:
		x != 0: Set auto-release time to x quarter-frames
		p is 0-1 or 6-7: Set dynamic auto-release
		p is 2-5: Disable auto-release
02: Rest for current note length. Acts as a rest if EITHER the unmodified byte OR byte + transpose value is 02. E.g. the command 9C 83 would set a transpose value of -2 semitones, and a 06 "note" would then resolve to a rest (6 - 4 = 2).
kkkk kkk0: Play key k + transpose value/2 for current note length. This sum cannot be 1.

Noise Channel Only:
DDpp pppp: Perform noise channel command p and DMC channel command D for current note length
	Noise channel:
		p = 1: Noise channel rests
		p > 1: Play noise preset p
	DMC channel:
		D = 1-2: Play DMC preset D
		Else: DMC channel rests
		
As previously stated, any byte immediately following a set length command is interpreted as a note/rest, allowing access to keys with the same values as other commands; however, as no known game uses keys outside the normally accessible range, this only (additionally) allows access to key code 0.

Some notes on the set timbre command are in order. The ctrl 1 register ($4000, $4004, etc.) value specified is the base value for the channel, and can be modified in a couple ways. For square wave channels, if the channel uses a volume envelope the bottom 4 bits of this value (the volume field) will be replaced by the current volume from the envelope. However the initially specified volume is retained, and will be restored if the envelope ends by restoring the base volume.

On the triangle channel the ctrl 1 register controls auto-release at the hardware level, and the set note length and set timbre commands fight over what is written to this register. The set timbre command sets the auto-release settings and ctrl 1 value as specified; the set note length command sets ctrl 1 BASED ON the current auto-release settings. The outcome will be different depending on the order of commands. If the set timbre command comes last, auto-release will be directly controlled by the ctrl 1 value specified, and the auto-release settings specified won't take effect until the next set note length command. If the set note length command comes last, the ctrl 1 value specified in the set timbre command will be completely overwritten based on the auto-release settings.

Examples

Square channel (current note length base offset is +4c: 90 BPM):
9F B3 31: Set timbre: envelopes and base ctrl 1
	p = 5: Pitch envelope 5
	x = $13: Volume envelope $13
	d = 0: Duty cycle 0 (12.5%)
	L = 1: Disable length counter
	V = 1: v is volume
	v = 1: Base volume 1. Will not actually be used as volume envelope $13 does not restore base volume.
D2: Begin loop
	n = $12: Play loop $12 times
B2: Set note length
	L = 2: Quarter note (40 frames)
1A x3: Notes
	k = $d: Key B2
B1: Set note length
	L = 1: 8th note (20 frames)
1A: Note
	k = $d: Key B2
1C: Note
	k = $e: Key C3
FF: End loop

Triangle channel of same track:
9F A0 00: Set timbre: pitch envelope, auto-release settings, and base ctrl 1
	1:x = 0: No explicit auto-release length
	1:p = 5: Pitch envelope 5. Auto-release disabled.
	2:F, 2:n: Ignored since set note length is done before notes are played
B7: Set note length. Also overwrites F and n from previous command with auto-release settings from p and x: disable auto-release.
	L = 7: Dotted 8th note (30 frames)
24: Note
	k = $12: Key E2 (triangle is 1 octave lower)
B0: Set note length
	L = 0: 16th note (10 frames)
02: Rest
	
Noise channel of same track:
D4: Begin loop
	n = $14: Play loop $14 times
B2: Set note length
	L = 2: Quarter note (40 frames)
41: Note event
	D = 1: Play DMC preset 1 (kick drum)
	n = 1: Noise channel rests
44: Note event
	D = 1: Play DMC preset 1
	n = 4: Play noise preset 4
41: Note event
	D = 1: Play DMC preset 1
	n = 1: Noise channel rests
07: Note event
	D = 0: DMC channel rests
	n = 7: Play noise preset 7
FF: End of loop

Square channel:
9C 8D: Set global transpose
	n = 1: Negative
	m = $d: Transpose value = -1 - $d = -$e (-7 semitones)
00: End of block

Triangle channel:
9F 0A 00: Set timbre: pitch envelope, auto-release settings, and base ctrl 1
	1:x = $a: Set duration until auto-release to $a quarter-frames
	1:p = 0: No pitch envelope
	2:F, 2:n: Ignored since set note length is done before notes are played
B3: Set note length
	L = 3: Half note (56 frames at current tempo). Notes will auto-release after 10 quarter-frames.
...
9F 00 00: Set timbre: pitch envelope, auto-release settings, and base ctrl 1
	1:x = 0: No explicit auto-release length
	1:p = 0: No pitch envelope. Do NOT disable auto-release; result: dynamic auto-release.
	2:F, 2:n: Ignored since set note length is done before notes are played
B3: Set note length
	L = 3: Half note (48 frames). Notes will auto-release after 15 frames.
...
B1: Set note length
	L = 1: 8th note (12 frames). Notes will auto-release after 11 frames.
	
Timbre and Envelopes

Depending on the channel, up to 3 types of timbre control exist in the Mother engine: the ctrl 1 register (especially the duty cycle for square wave channels), volume envelopes, and pitch envelopes, all of which are set by the set timbre command.

Volume envelopes in the Mother engine are fairly short non-looping sequences of volume values that end either by restoring the base volume for the channel or silencing the channel. To reduce the space required, the Mother engine packs 2 volume values into each byte of the envelope. The engine theoretically supports up to $1f volume envelopes, but Mother has $1b envelopes.

Examples

A8 76 FF: Short decay envelope into sustain. Frames 0-3 will have the volume values $a, 8, 7, 6, then the channel base volume will be used.

91 91 91 91 91 91 91 91 91 91 F0: Odd short, non-sustaining, 30 Hz tremolo envelope of center 5 and depth (center to peak) 4 that silences the channel after 20 frames (1/3 sec). 30 Hz is above the limit of hearing, so this will likely have a peculiar frequency modulation effect.

Pitch envelopes are the only truly janky feature of the Mother engine. They are a hybrid system that mixes period-linear absolute (i.e. not relative to the previous frame) period offset arrays with hard-coded behavior (including the length and loop points of the arrays). Making matters worse is the fact that on the triangle channel the "forever" field of the auto-release settings is encoded in the same bits as the pitch envelope number, meaning only certain envelope/auto-release setting combinations are possible. While it is entirely conceivable that the set of envelopes could be game-specific, all games I've investigated have had the same set of pitch envelopes.

A basic description of the pitch envelopes is as follows, showing the envelope number, "forever" field, and a basic description; for a more detailed description see the additional information section.

E  F  Description
1: 0  6 Hz vibrato with depth (center to peak) of 2 period units
2: 1  Slides period from 0 to -10 over $10 frames, performs 15 Hz depth 1 vibrato for 2 cycles, then sustains a constant -10 period offset
3: 1  Fixed -2 period offset
4: 1  Pitch slide from +9 to 0 period offset followed by 6 Hz depth 1.5 vibrato. Is NOT applied to key $23.
5: 1  6 Hz depth 2 vibrato that has a fade-in period of $21 frames
6: 0  Pitch slide from +9 to 0 period offset followed by 6 Hz depth 1.5 vibrato. Is NOT applied to key $23.
7: 0  6 Hz depth 2 vibrato

Additional Tables and Information

Track Table

Track bank 0: Header offset table 903e, header block base 906f:
   1 Eight Melodies @906f:  +24  +18  ffff  ffff   76c  ffff
    Triangle @ 76c: 92aa 92b1 92bc 92c7 92d3 92df 92e8 92f5 9301 0000

   2 Battle Theme 1 @9079:   +0  +28  9309  9311  931b  932d
    Square 1 @9309: 9592 | 9335
    Square 2 @9311: 95a4 | 940b 944e
    Triangle @931b: 95b6 | 94e7 94f9 94e7 94e7 94f9 952a
    Noise    @932d: 95c8 | 9543

   3 Battle Theme 2 @9083:   +0  +28  956e  9578  9582  958a
    Square 1 @956e: 9592 | 95cb 960d
    Square 2 @9578: 95a4 | 95ec 96b1
    Triangle @9582: 95b6 | 971f
    Noise    @958a: 95c8 | 977a

   4 Battle Theme 3 @908d:   +0  +28  979e  97a8  97b2  97be
    Square 1 @979e: 9592 | 97c8 9800
    Square 2 @97a8: 95a4 | 9814 9895
    Triangle @97b2: 95b6 | 98df 98fe 98f3
    Noise    @97be: 95c8 | 992b 992b

   5 Victory @9097:   +0   +0  995a  995e  9960  ffff
    Square 1 @995a: 9962 0000
    Square 2 @995e: 9971
    Triangle @9960: 9980

   6 Pollyanna (I Believe in You) @90ab:   +0  +35  9b0e  9b18  9b22  9b2a
    Square 1 @9b0e: 9b32 | 9bab 9bef
    Square 2 @9b18: 9b53 | 9c96 9ccd
    Triangle @9b22: 9b74 | 9d05
    Noise    @9b2a: 9b8c | 9c3f

   7 Bein' Friends @90a1:   +0  +28  9d84  9d90  9d9c  9da8
    Square 1 @9d84: | 9db4 9e29 9e29 9ec2
    Square 2 @9d90: | 9ddb 9e4e 9e4e 9f17
    Triangle @9d9c: | 9e07 9e72 9e72 9f5a
    Noise    @9da8: | 9e15 9eae 9eae 9fab

   8 Advent Desert @90b5:   -2   +c  998f  9997  999f  99a7
    Square 1 @998f: 99af | 99cb
    Square 2 @9997: 99b8 | 9a3d
    Triangle @999f: 99c1 | 9aea
    Noise    @99a7: 99c7 | 9b03

   9 Magicant @90bf:   +0  +4c  a083  a08b  a091  a09f
    Square 1 @a083: a0a5 | a0af
    Square 2 @a08b: | a0ac
    Triangle @a091: | a11b a127 a138 a138 a149
    Noise    @a09f: | a161

   a Snow Man @90c9:   +0  +35  a171  a187  a18d  ffff
    Square 1 @a171: a1fd | a207 a22c a207 a254 a272 a28c a272 a2a0
    Square 2 @a187: a203 ffff a173
    Square 2 @a173: | a207 a22c a207 a254 a272 a28c a272 a2a0
    Triangle @a18d: | a197 a197 a1d0

   b Mount Itoi @90d3:   +0  +4c  a2c4  a2ca  a2d0  a2d6
    Square 1 @a2c4: | a2dc
    Square 2 @a2ca: | a2f6
    Triangle @a2d0: | a33f
    Noise    @a2d6: | a36d

   c Factory @90dd:   +0  +35  a68e  a686  a698  a6a0
    Square 1 @a68e: a707 | a6b1 a6f4
    Square 2 @a686: | a6ae a6f1
    Triangle @a698: | a70d a716
    Noise    @a6a0: | a72a a73d a74f a73d a755

   d South Cemetery @90e7:   +0  +35  a37c  a384  a38c  a394
    Square 1 @a37c: a39c | a3fd
    Square 2 @a384: a3b4 | a3fa
    Triangle @a38c: a3cf | a443
    Noise    @a394: a3e2 | a46d

   e Twinkle Elementary School @90f1:   +0  +18  a480  a486  a48c  a492
    Square 1 @a480: | a498
    Square 2 @a486: | a4dc
    Triangle @a48c: | a508
    Noise    @a492: | a52e

   f Humoresque of a Little Dog @90fb:   +0  +18  a565  a56d  a573  a579
    Square 1 @a565: a621 | a582
    Square 2 @a56d: | a57f
    Triangle @a573: | a627
    Noise    @a579: | a65f

  10 Poltergeist @9105:   -8  +18  9fda  9fe4  9fee  9ff8
    Square 1 @9fda: a000 | a005 a01b
    Square 2 @9fe4: a023 | a023 a03e
    Triangle @9fee: a046 | a051 a05f
    Noise    @9ff8: a068 | ad5d

  11 Basement @910f:   +0  +28  a768  a770  a77c  a784
    Square 1 @a768: a78c | a7b1
    Square 2 @a770: a797 | a7be a7b4 a7e1
    Triangle @a77c: a7a2 | a7ec
    Noise    @a784: a7ac | a803

  12 My Home @9119:   +2  +43  a8ec  a8e6  a8f2  a8f8
    Square 1 @a8ec: | a939
    Square 2 @a8e6: | a903
    Triangle @a8f2: | a959
    Noise    @a8f8: | a8fe

  13 Cave 2 @9123:   +0  +35  a973  a97d  a985  a98d
    Square 1 @a973: a9b1 aa0a | aa12
    Square 2 @a97d: a995 | a9ef
    Triangle @a985: a9ca | aa2a
    Noise    @a98d: a9e2 | aa4c

  14 The Paradise Line @912d:   +0  +18  bb4f  bb63  bb6f  bb83
    Square 1 @bb4f: bb8b | bc34 bc34 bc48 bc34 bc34 bc48 bc5b
    Square 2 @bb63: bbb8 | bca5 bca5 bd03
    Triangle @bb6f: bbd9 | bd4d bd4d bd5b bd4d bd4d bd5b bd65
    Noise    @bb83: bc06 | bd86

  15 Fallin' Love @9137:   +0  +43  aa75  aa83  aa8d  aa93
    Square 1 @aa75: | aabd aac5 aac1 aac5 aaa7
    Square 2 @aa83: aa99 | aa9d aad4
    Triangle @aa8d: | ab0c
    Noise    @aa93: | ab1b

  16 Mother Earth @9141:   +0  +28  ba33  ba2d  ba39  ba3f
    Square 1 @ba33: | ba9c
    Square 2 @ba2d: | ba45
    Triangle @ba39: | bb17
    Noise    @ba3f: | bb49

  17 Tank @914b:   +0  +18  ab37  ab47  ab55  ab5d
    Square 1 @ab37: | abce abd6 abd6 abe8 ac43 ab7a
    Square 2 @ab47: | ac0a ac12 ac12 ac24 ab65
    Triangle @ab55: | acf3 ab95
    Noise    @ab5d: | ad3d abb2

  18 Ruins of Desert @9155:   +0   +c  a80c  a814  a81a  ffff
    Square 1 @a80c: | a820 a827
    Square 2 @a814: | a824
    Triangle @a81a: | a892

Track bank 1: Header offset table 9056, header block base 915f:
  19 Queen Mary's Song @915f:   +0  +28  addb  adc3  ffff  ffff
    Square 1 @addb: ade5 ffff adc5
    Square 1 @adc5: | 92b1 92bc 92c7 92d3 92df 92e8 92f5 9301 ade1
    Square 2 @adc3: adeb | 92b1 92bc 92c7 92d3 92df 92e8 92f5 9301 ade1

  1a Wisdom of the World @9169:   +0  +5a  ae52  ae58  ae5e  ffff
    Square 1 @ae52: | ae64
    Square 2 @ae58: | aec0
    Triangle @ae5e: | af21

  1b Tombstone @9173:  +24  +4c  b0e5  b0dd  ffff  ffff
    Square 1 @b0e5: b0f1 | 9c99
    Square 2 @b0dd: | b0ed 9c99

  1c Game Over @917d:   +0  +4c  b0f8  b100  b108  ffff
    Square 1 @b0f8: b10c b115 ffff b102
    Square 1 @b102: | b11f
    Square 2 @b100: b112 | b11f
    Triangle @b108: b12f 0000

  1d Big Victory @9187:   +0  +18  b147  b14b  b14d  ffff
    Square 1 @b147: b14f 0000
    Square 2 @b14b: b161
    Triangle @b14d: b175

  1e Airplane @9191:   +0  +18  af4e  af54  af5a  af6c
    Square 1 @af4e: | af72
    Square 2 @af54: | afb2
    Triangle @af5a: | affd b02e b02e b09d b0ba b09d b0c4
    Noise    @af6c: | b03d

  1f Level Up @919b:   +6   +0  ae1e  ae28  ae30  ffff
    Square 1 @ae1e: b14f ae38 | ae43
    Square 2 @ae28: b161 | ae40
    Triangle @ae30: b175 | ae4f

  20 Recovery @91a5:   -4  +18  adef  adf3  adf5  ffff
    Square 1 @adef: adf7 0000
    Square 2 @adf3: ae04
    Triangle @adf5: ae10

  21 Fanfare @91af:   -4  +43  b51e  b522  b524  ffff
    Square 1 @b51e: b532 0000
    Square 2 @b522: b526
    Triangle @b524: b53f

  22 Live House @91b9:   -8  +18  b184  b18a  b196  b1a2
    Square 1 @b184: | b1a8
    Square 2 @b18a: | b1c4 b1c4 b1da b1c4
    Triangle @b196: | b1ed b1ed b201 b1ed
    Noise    @b1a2: | b212

  23 All That I Needed (Was You) @91c3:   +0  +18  b222  b238  b248  b25a
    Square 1 @b222: b2c5 b2d9 b2d9 b31e b329 b329 b329 b34e b2d9 b31e b25e b2ae
    Square 2 @b238: b2ae b37b b3b5 b37b b3b8 b37b b272 0000
    Triangle @b248: b2d1 b426 b426 b443 b446 b446 b453 b426 b29b
    Noise    @b25a: b46a b491

  24 Melody 1 - Doll @91cd:  +48  +28  9259  925d  ffff  ffff
    Square 1 @9259: 929e 92b1
    Square 2 @925d: 92ae 0000

  25 Melody 2 - Canary @91d7:  +24  +28  9261  9265  ffff  ffff
    Square 1 @9261: 92a4 92bc
    Square 2 @9265: 92b9 0000

  26 Melody 3 - Monkey @91e1:   +0  +28  9269  926d  ffff  ffff
    Square 1 @9269: 92a4 92c7
    Square 2 @926d: 92c4 0000

  27 Melody 4 - Piano @91eb:   +0  +28  9271  9275  ffff  ffff
    Square 1 @9271: 929e 92d3
    Square 2 @9275: 92d0 0000

  28 Melody 5 - Cactus @91f5:  +48  +28  9279  927d  ffff  ffff
    Square 1 @9279: 92a4 92df
    Square 2 @927d: 92dc 0000

  29 Melody 6 - Dragon @91ff:  +24  +28  9281  9285  ffff  ffff
    Square 1 @9281: 92a4 92e8
    Square 2 @9285: 92e5 0000

  2a Melody 7 - EVE @9209:  +48  +28  9289  928d  ffff  ffff
    Square 1 @9289: 929e 92f5
    Square 2 @928d: 92f2 0000

  2b Melody 8 - Tombstone @9213:  +24  +28  9291  9295  ffff  ffff
    Square 1 @9291: 92a4 9301
    Square 2 @9295: 92fe 0000

  2c Giegue @921d:   +0  +43  b547  b54d  ffff  ffff
    Square 1 @b547: | b553
    Square 2 @b54d: | b559

  2d Ending @9227:   +0  +28  b8c0  b8b2  b8d4  b8e2
    Square 1 @b8c0: b6df b931 b67c b781 b7c7 b825 b69d | b6df
    Square 2 @b8b2: b6a0 b8f0 b666 b72e | b6a0
    Triangle @b8d4: b724 b9ff b693 b83b | b724
    Noise    @b8e2: b729 ba23 b698 b882 | b729

  2e Choucream Zoo @9231:   +0  +28  b55f  b565  a77e  a786
    Square 1 @b55f: | b56b
    Square 2 @b565: | b573
    Triangle @a77e: | a7ec
    Noise    @a786: | a803

  2f Phone @923b:   +0  +18  ffff  b57b  ffff  ffff
    Square 2 @b57b: | b581

  30 Youngtown @9245:   +0  +28  b589  b58f  b595  ffff
    Square 1 @b589: | b5a1
    Square 2 @b58f: | b5cd
    Triangle @b595: | b602

  31 Cave 1 @924f:   +0  +28  b63c  b644  ffff  ffff
    Square 1 @b63c: b64a | b653
    Square 2 @b644: | b650
	
Reading the table:

  31 Cave 1 @924f:   +0  +28  b63c  b644  ffff  ffff
- Track number $31. Note that this is the number used to play the track in game. To get the track's index in the bank header offset arrays, subtrack 1 or $19 from tracks in the 2 banks. Thus this is $31 - $19 = index $18 in the bank 1 header offset array.
- Track name "Cave 1"
- Track header address $924f
- +0 initial transpose value in decimal (+0/2 = +0 semitones)
- Initial note length table base offset $28 (~129 BPM)
- Square 1 playlist address $b63c, square 2 $b644
- No triangle or noise channel data for this track

    Square 1 @b63c: b64a | b653
- Square 1 playlist starting at address $b63c
- Plays block $b64a, then repeatedly plays block $b653. The playlist is terminated by ffff b63e which loops as shown, but this is hidden to make the playlist more readable.

    Square 1 @9291: 92a4 9301
    Square 2 @9295: 92fe 0000
- Square 2 channel terminates the track with an end of track command
- Square 1 is terminated implicitly by square 2, and has no terminator of its own

    Square 2 @a187: a203 ffff a173
    Square 2 @a173: | a207 a22c a207 a254 a272 a28c a272 a2a0
- Square 2 channel has 2 playlist segments due to a goto command
- The goto is not hidden because it does not loop but goes to a different playlist segment. The second playlist segment does loop so its terminator is hidden.

   1 Eight Melodies @906f:  +24  +18  ffff  ffff   76c  ffff
    Triangle @ 76c: 92aa 92b1 92bc 92c7 92d3 92df 92e8 92f5 9301 0000

Track 1 is very special. Its triangle channel points into RAM, as the playlist is constructed dynamically. This is the Eight Melodies track, and it is made up of 8 pieces of the melody (the inner 8 blocks). Depending on whether a piece has been picked up in game, the block will either be as shown here or a placeholder beep.

The base (no pieces acquired) version of this track is copied from 1c:8217 ($a words) during initialization. Game-specific code in the begin track process then selects either the melody piece from 1c:822b (8 words) or the placeholder beep (block address $9299) for each piece:

823B    LDA $761E
823E    STA $B0
8240    LDY #$00
8242    BEQ $8250
8244    LDA #$99
8246    STA $076E,Y
8249    INY
824A    LDA #$92
824C    STA $076E,Y
824F    INY
8250    TYA
8251    CMP #$10
8253    BEQ $8269
8255    LSR $B0
8257    BCC $8244
8259    LDA $822B,Y
825C    STA $076E,Y
825F    INY
8260    LDA $822B,Y
8263    STA $076E,Y
8266    INY
8267    BNE $8250
8269    RTS

1c:8fd6 byte[$68?]: Note length table in frames

Code to load the current length for notes:
8CAA    LDA $8FD6,Y

Code to limit the triangle auto-release length to 15 frames ($3c quarter-frames) when in dynamic auto-release mode:
8D73    CMP #$3C
8D75    BCC $8D79
8D77    LDA #$3C

1c:8f4c big-endian word[$43]: Key pitch table, in period register units. For square wave channels, period = 1789773 / frequency / 16 - 1 (triangle channel is 1 octave lower). Entry 1 must be 0 as it is rest.

Code to load the period for a key:
8CC6    LDA $8F4D,Y
...
8CE1    LDA $8F4D,Y
8CE4    STA $0780,X
8CE7    LDA $8F4C,Y
8CEA    ORA #$08
8CEC    STA $0781,X

1c:8928 byte[$1f?]: Noise presets table. Data actually starts at offset 1 ($b201), and is NOT an array, as some entries overlap. The first byte should always be $10 as preset 1 is rest.
	+0 byte: Ctrl 1 value
	+1 word: Period regs value
	
Code to play a noise preset:
8D93    LDA $8928,Y
8D96    STA NoiseVolume_400C
8D99    LDA $8929,Y
8D9C    STA NoisePeriod_400E
8D9F    LDA $892A,Y
8DA2    STA NoiseLength_400F

Code to play a DMC preset if any:
8DA6    TYA
8DA7    AND #$C0
8DA9    CMP #$40
8DAB    BEQ $8DB2
8DAD    CMP #$80
8DAF    BEQ $8DBC
8DB1    RTS
8DB2    LDA #$0E  <- preset 1: kick drum
8DB4    STA $B1
8DB6    LDA #$07
8DB8    LDY #$00
8DBA    BEQ $8DC4
8DBC    LDA #$0E  <- preset 2: snare drum
8DBE    STA $B1
8DC0    LDA #$0F
8DC2    LDY #$02
8DC4    STA DmcLength_4013
8DC7    STY DmcAddress_4012
8DCA    LDA $07F7
8DCD    BNE $8DE3
8DCF    LDA $B1
8DD1    STA DmcFreq_4010
8DD4    LDA #$0F
8DD6    STA ApuStatus_4015
8DD9    LDA #$00
8DDB    STA DmcCounter_4011
8DDE    LDA #$1F
8DE0    STA ApuStatus_4015
8DE3    RTS

Volume Envelope Table

1c:8ded word[$1b]: Volume envelope table. Indices are 0-based, unlike in the set timbre commands and the following table.

Envelope  1 @8e4f: 233456776554 ff
Envelope  2 @8e56: 5a9888776666655555 ff
Envelope  3 @8e76: 111122223333444444455555556666777888 ff
Envelope  4 @8e89: f987777766655544 ff
Envelope  5 @8e92: a876 ff
Envelope  6 @8e98: 99 ff
Envelope  7 @8e48: 235678888887 ff
Envelope  8 @8e9a: dcba998887765544 ff
Envelope  9 @8ea3: 2344333333333332 ff
Envelope  a @8e95: 7432 ff
Envelope  b @8eac: 7776655544433221 f0
Envelope  c @8eb5: 44433332221111 f0
Envelope  d @8ebd: 33332222111111 f0
Envelope  e @8ec5: 222222111111 f0
Envelope  f @8ecc: 1111111111110100 f0
Envelope 10 @8ed5: 998877766655544433333332222222222111111111111111 f0
Envelope 11 @8f20: 23455544333322 ff
Envelope 12 @8f28: 87654321443321113221111121111111111111 ff
Envelope 13 @8eee: 6555544433333333222222221111111111111111 f0
Envelope 14 @8f3c: 666542213221111121111111111111 ff
Envelope 15 @8f03: fbbaaa99999998887777776666665554444443333322222222111111 f0
Envelope 16 @8e23: 7611111431 ff
Envelope 17 @8e60: 111122223333444444455555556666777888765432 ff
Envelope 18 @8e3f: 9876632287765311 f0
Envelope 19 @8e38: 233332222222 ff
Envelope 1a @8e2d: 91919191919191919191 f0
Envelope 1b @8e29: 334566 ff

Code to load an envelope address:
8B28    LDA $8DED,Y
8B2B    STA $B2
8B2D    LDA $8DEE,Y
8B30    STA $B3

Pitch Envelopes

Pitch envelopes are difficult to describe as they're a mixture of data and code. To start with, the simple envelopes that just do vibrato, #5 with a fade in (for convenience period offsets are in decimal):

Envelope 1 @8a33: | +0 +1 +1 +2 +1 +0 -1 -1 -2 -1
Envelope 5 @8a12: +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +1 +0 +0 +0 +0 -1 +0 +0 +0 +0 +1 +1 +0 +0 +0 -1 -1 +0 | +0 +1 +1 +2 +1 +0 -1 -1 -2 -1
Envelope 7 @8a33: | +0 +1 +1 +2 +1 +0 -1 -1 -2 -1

Envelope 2 is effectively as follows, but the loop at the end is actually hard-coded:

Envelope 2 @8a3d: +0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -10 -9 -10 -11 | -10

Envelope 3 is hard-coded to -2 period units. Oddly, it checks whether the key number is < $4c/2 = $26, but then sets the offset to -2 in both cases.

Envelopes 4 and 6 are simple (identical) vibrato envelopes, but hard-coded to NOT apply to key $46/2 = $23:

Envelope 4 @8a06: +9 +8 +7 +6 +5 +4 +3 +2 +2 +1 +1 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +1 +0 +0 +0 +0 -1 +0 +0 +0 +0 +1 +1 | +0 +0 +0 -1 -1 +0 +0 +1 +1 +2
Envelope 6 @8a06: +9 +8 +7 +6 +5 +4 +3 +2 +2 +1 +1 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +1 +0 +0 +0 +0 -1 +0 +0 +0 +0 +1 +1 | +0 +0 +0 -1 -1 +0 +0 +1 +1 +2

The weirdness on envelopes 3, 4, and 6 are found on all games using this engine that I've investigated.

The code. It actually starts at $89b4, with the pitch envelope index in the high 3 bits of $b0 and the current index into the envelope in $b2:
8977    LDA $B2     <- envelopes 4 and 6
8979    CMP #$31
897B    BNE $897F
897D    LDA #$27
897F    TAY
8980    LDA $8A06,Y
8983    PHA
8984    LDA $07C3,X
8987    CMP #$46
8989    BNE $8990
898B    PLA
898C    LDA #$00    <- hard-coded +0 pitch adjustment if current key number is $46/2 = $23
898E    BEQ $89EE
8990    PLA
8991    JMP $89EE
8994    LDA $B2     <- envelope 2
8996    TAY
8997    CMP #$10
8999    BCS $89A1
899B    LDA $8A3D,Y
899E    JMP $89F4
89A1    LDA #$F6
89A3    BNE $89F4
89A5    LDA $07C3,X <- envelope 3
89A8    CMP #$4C    <- utterly pointless key number check as both paths are the same
89AA    BCC $89B0
89AC    LDA #$FE
89AE    BNE $89F4
89B0    LDA #$FE
89B2    BNE $89F4
...
89B4    LDA $07D1,X <- actually starts here
89B7    STA $B2
89B9    LDA $B0
89BB    CMP #$20
89BD    BEQ $89D3 <- envelope 1 branch
89BF    CMP #$A0
89C1    BEQ $89E2 <- envelope 5 branch
89C3    CMP #$60
89C5    BEQ $89A5 <- envelope 3 branch
89C7    CMP #$40
89C9    BEQ $8994 <- envelope 2 branch
89CB    CMP #$80
89CD    BEQ $8977 <- envelope 4 branch
89CF    CMP #$C0
89D1    BEQ $8977 <- envelope 6 branch
89D3    LDA $B2   <- envelopes 1 and 7
89D5    CMP #$0A
89D7    BNE $89DB
89D9    LDA #$00
89DB    TAY
89DC    LDA $8A33,Y
89DF    JMP $89EE
89E2    LDA $B2   <- envelope 5
89E4    CMP #$2B
89E6    BNE $89EA
89E8    LDA #$21
89EA    TAY
89EB    LDA $8A12,Y
89EE    PHA
89EF    TYA
89F0    STA $07D1,X
89F3    PLA
89F4    PHA         <- common path
89F5    LDA $07C8,X
89F8    BNE $8A04   <- don't mess with it if a sound effect is playing
89FA    PLA
89FB    CLC
89FC    ADC $B1
89FE    LDY $BE
8A00    STA Sq0Timer_4002,Y
8A03    RTS
8A04    PLA
8A05    RTS

The code that determines whether a given envelope has the triangle "forever" flag set:
8D5C    LDA $079C <- pitch envelope in top 3 bits
8D5F    AND #$C0
8D61    BNE $8D66
8D63    TYA
8D64    BNE $8D6E
8D66    CMP #$C0
8D68    BEQ $8D63
8D6A    LDA #$FF  <- forever. Either bit 6 or 7 is set, but not both.