SYN file format: SimSynth patch, version 1

Introduction

Version 1 of the patch file of SimSynth, the first subtractive synthesizer of FruityLoops. A patch holds three oscillators, an LFO, three envelopes of five points and a block of settings, in exactly 989 bytes. It is the same structure as version 2 with everything cut down: the records are 220 bytes instead of 286, the envelopes 22 bytes instead of 1,266, and there is no riff and no comment. FruityLoops 3 ships files of this version (its SS_Instruments and SS_Effects folders hold 73 different ones). Its ss2wav.dll refuses a version below 2 with an error code, and the 16-bit ss2wav16.dll beside it is presumably the reader of version 1.

The format is not published. The sizes are certain: they add up to the file size exactly, and all 146 real files (73 different ones) on this site’s machine fit. The record and envelope layouts are the version 2 layout of the loader in ss2wav.dll, cut down; they were matched to the real files (the defaults and the value ranges agree) but the version 1 loader itself was not read. The names of fields are inferred, as on the version 2 page, and the last block is listed by position only.

Structure

0x0000Header SYNTH, the version 1 and a revision9 bytes
0x0009Records oscillator 1, 2, 3 and the LFO4 × 220 bytes
0x0379Envelopes three, each five times, five levels and a flag3 × 22 bytes
0x03BBSettings 17 words34 bytes

A SimSynth version 1 patch, in file order: 989 bytes

All numbers are little-endian 16-bit words, signed where a field can be negative.

Header

Offset	Size	Field	Meaning
`0x00`	5	Signature	The characters `SYNTH`
`0x05`	2	Version	1
`0x07`	2	Revision	2 (28 files) or 3 (45 files). The same field the version 2 loader uses to bring old files up to date; what it means in version 1 is not known

Oscillator and LFO records

Four records of 220 bytes from 0x0009, at 0x0009, 0x00E5, 0x01C1 and 0x029D: oscillator 1, 2 and 3, then the LFO. The ten words are those of version 2; the text buffer at the end is 200 bytes instead of 266.

Offset	Size	Field	Meaning
`0x00`	2	Detune (inferred), signed	Zero in most patches; 3, 8, −1, 100, 300 and 500 are seen
`0x02`	2	Level (inferred)	0 to 99. 50 (24 of the 73 files’ first oscillators) and 99 (29) are the common values
`0x04`	2	Pitch offset (inferred), signed	In cents: 0, ±1200, 2400, 700 and others. In the LFO record usually 12, which looks like its rate
`0x06`	2	Pulse width (inferred)	0 to 255; 255 in 65 of the 70 first oscillators and in every LFO
`0x08`	2	Amount (inferred), signed	A modulation amount: 0, ±100, ±500 and others
`0x0A`	2	Off switch (inferred)	0 or 1; always 0 in oscillator 1, 1 in oscillators 2 and 3 of most files
`0x0C`, `0x0E`, `0x10`	2 each	Switches 1, 2 and 3 (inferred)	Each 0 or 1
`0x12`	2	Shape (inferred)	0 to 4; 1 or 2 in most
`0x14`	200	Wave file path	Zero-terminated text: `NA` when there is none. 12 files hold a path such as `C:\SIMSYNTH\WHONK.OSC` or `C:\ZAPP\WAVEY\ORGAN.OSC` in an oscillator whose shape is 2 or 4

Envelopes

Three envelopes of 22 bytes from 0x0379: five times, five levels and a flag. A new patch has the points time 0, level 255 and time 400, level 0 in each, and the flag 0 in the first and 1 in the other two, as in version 2.

Offset	Size	Field
`0x00`	10	Times (inferred): five words
`0x0A`	10	Levels (inferred): five words, 0 to 255
`0x14`	2	Flag (inferred)

Settings

The last 34 bytes, from 0x03BB, are 17 words. They hold the filter, amplifier and chorus values, which version 2 keeps in its settings blocks, but which word is which is not worked out. In the blank patch the first is 128, the next two 0, the fourth and fifth −128, and the later words include 48, 302, 3,097 (0x0C19) and 8,788 (0x2254); the last two are defaults that the version 2 loader also uses.

Worked example

The start of VIBE.SYN, from FruityLoops 3’s SS_Instruments:

0000: 53 59 4E 54 48  01 00  03 00   SYNTH, version 1, revision 3
0009: 03 00           detune 3
000B: 63 00           level 99
000D: 00 00           pitch offset 0
000F: FF 00           pulse width 255
0011: 00 00  00 00    amount 0, off switch 0
0015: 00 00  00 00  00 00   switches 0, 0, 0
001B: 02 00           shape 2
001D: 4E 41 00 …      wave file path "NA"
00E5:                 oscillator 2 begins (0x9 + 220)

Telling it apart

The file starts with SYNTH and the word 1 at offset 5, and is exactly 989 bytes long. Version 2 has a 2 there and is 6,763 bytes. Other programs’ .syn files do not start with SYNTH.

Not described

This page is partial: the file has no published specification, and these things are guessed or unknown, in the reference and in the viewer.

Item	Reference	Viewer
The version 1 loader	Not read: the layout was matched to real files and to the version 2 loader, not taken from `ss2wav16.dll`	Reads only files of exactly 989 bytes
Record fields	Names and meanings are inferred from defaults and value ranges; the shape values are not named	Shows the numbers with “inferred” in the name
Envelopes	What the flag does and which envelope drives what are not known	Lists the five points; draws no picture
Settings (17 words)	Position only; no word is named	Shows them as unnamed words
Revision	What 2 and 3 mean in version 1 is not known	Shows the number only
Wave files	The format of the `.OSC` files the paths name is not described	Shows the path as text, does not open the file

Variants

SimSynth patch, version 1 – 989-byte patches of the first SimSynth, with five-point envelopes
SimSynth patch, version 2 – 6,763-byte patches of SimSynth 2 and SimSynth Live, with 300-point envelopes, a riff and a comment

.SYN File Format