Sonic Jam/Sounds

SCHG: Sonic Jam
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PCM Samples

According to my research so far, all PCM samples are big-endian, and monaural. Most are in a signed 8-bit format, with a sample rate of 22050Hz. However, some are in a signed 16-bit format, with a sample rate of 11025Hz. These are noted accordingly.

SWORLD.SND Map

Here's a map of PCM samples that can be found in SWORLD.SND. Start and end addresses are inclusive; they're part of the sample.

Bank 1:

Start Address	End Address	Description	Notes
$004A6	$02D5D	Flute (Low)
$02D5E	$06A7B	Flute (High)
$06A7C	$073B1	Bass Drum
$073B2	$08D53	Snare Drum	16-bit.
$08D54	$0967F	Open Conga Drum	Used for both the Open High Conga and Open Low Conga.
$09680	$09CDB	Muted High Conga Drum
$09CDC	$0B189	Taiko Drum?	Used for MIDI key 87.
$0B18A	$0C499	Tambourine
$0C49A	$0CFD1	Side Stick	Used for both the Side Stick, and MIDI key 86 (Taiko Side Stick?).
$0CFD2	$0FF91	Crash Cymbal	16-bit.
$0FF92	$112B1	Bass Guitar	16-bit.
$112B2	$120F1	Trumpet
$120F2	$14D31	Brass
$14D32	$1512F	Sawtooth	16-bit. Used for the Synth Brass program, one of the leads for the Sonic World BGM.
$15130	$1670F	Steel Drum
$16710	$1CB3B	Tom Drum	16-bit.
$1CB3C	$215BB	Piano (Low)
$215BC	$2611D	Piano (High)
$2611E	$2982F	Voice Oohs	Used in two programs, one alone ($0B), and one composited with the Electric Piano sample ($07).
$29830	$2AD8F	Electric Piano	Used in two programs, one alone ($0C), and one composited with the Voice Oohs sample ($07).
$2AD90	$2EEC7	Synth Strings
$2EEC8	$2F287	Oboe	One of the leads for the Building BGM.
$2F288	$2F2AF	Unknown	Inaudible. Key 58 of the drum program; this could be a placeholder for/remnants of a Vibraslap sample.

Bank 2:

Start Address	End Address	Description	Notes
$2F94E	$2FEDD	Menu Cancel	Modulated like crazy to make the SFX.
$2FEDE	$311FD	Menu Confirm	Not full sound, just the sample used to play it.
$311FE	$3234D	Game Cart Select	For the games collection.
$3234E	$3294D	S&K Lock On
$3294E	$32BAF	Menu Select/Mission Button
$32BB0	$358D1	Warp Noise	The special stage transition sound from the classics. Used for the Big Ring.
$358D2	$35B21	Square Wave	16-bit. Layered on itself to composite the Skidding SFX.
$35B22	$36525	Landing 1	Part of the SFX for Sonic landing on the ground. Composited with Landing 2.
$36526	$36E67	Landing 2	Part of the SFX for Sonic landing on the ground. Composited with Landing 1.
$36E68	$37043	Checkpoint	Low pitched. Double sample rate?
$37044	$37A0F	Spring	High pitched. Half sample rate?
$37A10	$381FB	Sine Wave	16-bit. Used for the Secret Point trumpets, an FM instrument.
$381FC	$399F9	Code Monitor Interact
$399FA	$39B03	Door Open	High pitched. Half sample rate?
$39B04	$3BE83	Wind	Unused.
$3BE84	$3DCF3	Honk/Door Creak	Unused.
$3DCF4	$3FBDF	Leaf Rustling
$3FBE0	$40021	Tails Flight
$40022	$423D1	Rock Organ	16-bit.
$423D2	$44DD1	Splash
$44DD2	$46E63	Waterfall
$46E64	$4A863	Ring Pick-up
$4A864	$4C6F7	Balloon Pop
$4C6F8	$4C71F	Unknown	Inaudible. Looks to be used by programs that are silent. Placeholder?
$4C720	$4ED8D	Jump

Music and SFX

The music in Sonic World (and interestingly, the SFX in both Sonic World and the Genesis ports) is performed in real-time via a variation of the MIDI standard (as opposed to just playing back a prerecorded audio file).

A Saturn MIDI file (at least as Sonic Jam handles them) consists of a Header, and a series of Tracks, which consist of a Tempo Track, and Play Data.

MIDI Header

A MIDI Header is very simple, consisting of only two components:

Function	Size	Notes
Number of Tracks	word
Offset of Track 1	long	From the top of the header.
Offset of Track 2	long	From the top of the header.
etc.

Tempo Track

A Tempo Track defines the Resolution of a track, the Tempo, any Tempo Changes that occur, and when they happen.

Function	Size	Notes
Resolution	word	Number of MIDI ticks per quarter-note (typically $01E0). Holding all else equal, lowering the value will slow the apparent tempo. Must be between $0018 and $03C0, inclusive, otherwise the song won't play.
Number of Tempos	word	The number of Tempo Duration and Tempo pairs defined below. Must have at least 1 pair.
Length of Tempo Track	word	In bytes. Counting starts at MSB of Resolution.
Length of Tempo List	word	In bytes. Counting starts at MSB of first Tempo Duration. Must be a multiple of 8 (4 bytes for each Tempo Duration, 4 bytes for each Tempo).
Tempo 1 Duration	long	The amount of time (in MIDI ticks) to play the song at the following tempo for, before changing to the next tempo (when applicable; otherwise this is ignored).
Tempo 1	long	Tempo to play the song at, in microseconds per quarter-note.
Tempo 2 Duration	long
Tempo 2	long
etc.

Any tempo changes done within a loop won't work as intended on subsequent loops. The progression of tempos only goes forward, won't jump backwards when a loop is triggered, and the last tempo will play forever rather than wrapping back to the start of the list. This looks to be intentional, reading the Saturn docs.

Play Data

The Play Data of a track consists of a continuous series of MIDI events. Each MIDI event consists of a Status byte, and a variable number of parameter bytes, ranging from 0 to 4. All possible MIDI events are defined below.

$00 - $7F: Note On

For Note On events, the upper nybble of Status is bit flags.

Bit Mask	Function
$10	Mutes the note when set, essentially changing this event to a rest.
$20	Extension bit for Delta Time parameter.
$40	Extension bit for Length parameter.

The lower nybble of Status is the channel to play the note on.

Note On events have 4 parameters.

Parameter	Function	Notes
$01	Pitch	Middle C is $3C.
$02	Volume	Clamped from $00 to $7F.
$03	Length	How long the note plays, in MIDI ticks.
$04	Delta Time	How long to wait before triggering this event, in MIDI ticks.

$80 - $8F: Song Flow

These events are for manipulating the song's flow.

Status	Event	Parameters	Notes
$80	Invalid	N/A	Abruptly terminates the song, cutting off any active notes.
$81	Reference?	3: Offset (High), Offset (Low), Count	Copies [Count] events, starting with the one at [Offset] from the start of the track. Needs confirmation.
$82	Loop Start/End	1: Delta Time	First call is where loop starts, second call is where the loop ends. Delta Time is in MIDI ticks.
$83	End Song	0	Immediately ends the song, letting any active notes play out.
$84 - $87	Invalid	N/A	Has the same behavior as event $80.
$88	Quarter Note Extend	0	Adds the length of a quarter note to the next Note On (can stack).
$89	Whole Note Extend	0	Like $88, but the length of a whole note.
$8A	2x Whole Note Extend	0	Like $88, but the length of two whole notes.
$8B	4x (and a Quarter) Note Extend	0	Like $88, but the length of four whole notes, plus a quarter. Could probably do with a double-check, that length seems strange.
$8C	One-eighth rest	0	Adds the delta time of an eighth rest to the next Note On (can stack).
$8D	Quarter rest	0	Ditto, for a quarter note.
$8E	Whole rest	0	Ditto, for a whole note.
$8F	2x Whole rest	0	Ditto, for two whole notes.

$90 - $9F: Invalid

On testing, these all seem to behave the same as event $80.

$A0 - $AF: Unused

The MIDI Standard and the Saturn’s docs seem to imply these are supposed to be Polyphonic Key Pressure events; however, the Saturn docs state (inconsistently) that this is unimplemented. Maybe this is just a ghost of that? I certainly don’t notice any difference when I fiddle around with it.

For any who wish to play around with them, they have 3 parameters, the last of which is Delta Time.

$B0 - $BF: Control Change

For Control Change events, the lower nybble of Status is the channel to change the control for.

Control Change events have 3 parameters.

Parameter	Function	Notes
$01	Control ID	The control to change. Could use some investigation and documenting.
$02	Value	The value to set the control to.
$03	Delta Time	How long to wait before triggering this event, in MIDI ticks.

$C0 - $CF: Program Change

For Program Change events, the lower nybble of Status is the channel to change the program for.

Program Change events have 2 parameters.

Parameter	Function	Notes
$01	Program	The program to change the channel to. Could use some investigation and documenting.
$02	Delta Time	How long to wait before triggering this event, in MIDI ticks.

$D0 - $DF: Unused

Similar to the $A_ events. Docs imply they are an unimplemented ghost of Channel Pressure. I can’t notice any changes when I fiddle with it.

2 parameters, the last is Delta Time.

$E0 - $EF: Pitch Wheel

For Pitch Wheel events, the lower nybble of Status is the channel to apply the pitch wheel to.

Pitch Wheel events have 2 parameters.

Parameter	Function	Notes
$01	Pitch	The pitch to set the wheel to. Could use some investigation and documenting.
$02	Delta Time	How long to wait before triggering this event, in MIDI ticks.

$F0 - $FF: System Events

I've yet to see any of these in use, and none of them seem particularly useful for ROM hacking purposes (assuming the docs are accurate).

If someone wants to document them, feel free.