ProTracker 3.6 module (IFF)

Introduction

ProTracker 3.59, in 1996, could save a module in a file of a new form: an IFF file, the same outer shape as Amiga pictures and sounds, holding the song’s version, some information about it, a comment and the module itself. Later versions to 3.62 write it too. The module inside is an ordinary ProTracker module, so the wrapper is the only thing a reader must add.

No specification of the wrapper was published; what follows is from OpenMPT’s loader for it, which is the source of everything here.

A .mod file of this kind dropped on any page of this site opens in the explorer, which shows each chunk and gives the embedded module an Open button; opened, it is read and played as any other module.

Structure

A 12-byte header, then chunks, one after the other to the end of the file. All numbers are big-endian.

Offset	Size	Field	Meaning
0	4	magic	`FORM`
4	4	size	The form size. OpenMPT does not check it.
8	4	type	`MODL`

Each chunk is an 8-byte header, four letters and a 32-bit size, then its data. The size of a chunk counts the 8-byte header, and the first chunk’s also counts the four bytes of MODL: subtract 8 for the data length, and 4 more for the first chunk. A chunk with another name is skipped.

VERS: the version

Offset	Size	Field	Meaning
0	4	skipped	Skipped.
4	2	magic	`PT`
6	rest	version	Text, such as `3.61`. If there is none, 3.6 is assumed.

INFO: the song

The chunk must be exactly 64 bytes:

Offset	Size	Field	Meaning
0	32	name	The song’s name, up to 32 characters; if the first byte is not 0 it replaces the title in the module.
32	2	samples	Read by OpenMPT but not used.
34	2	orders	Read by OpenMPT but not used.
36	2	patterns	Read by OpenMPT but not used.
38	2	volume	If not 0, a sample pre-amp, at most 64.
40	2	tempo	If not 0 and the song does not use vertical-blank timing, the default tempo.
42	2	flags	Bit 8 (`0100`) set means CIA timing; clear means vertical-blank timing.
44	12	date saved	Six 16-bit numbers: day, month, year since 1900, hour, minute and second.
56	8	playing time	Four 16-bit numbers: hours, minutes, seconds and milliseconds. Read by OpenMPT but not used.

CMNT: author and comment

Offset	Size	Field	Meaning
0	32	author	Text. `UNNAMED AUTHOR` means none.
32	rest	comment	Text, wrapped to lines of 40 characters.

PTDT: the module

The chunk’s data is a whole module, starting with the module’s title. OpenMPT reads more than the chunk’s stated size, because some files record their sample sizes wrongly. A reader should use the size only as a guide and read the module by its own header. OpenMPT plays the module with vertical-blank timing if the flags say so, and with the pre-amp and tempo from INFO.

Also used for

Go module file – A Go module's path, Go version and dependencies, as line-oriented UTF-8 text.

Variants

ProTracker module (M.K.) – 31 samples and 4 channels, marked M.K. at offset 1080: the standard Amiga module
Multichannel module (xCHN, xxCH) – 31 samples and any channel count other than 4, marked 6CHN, 8CHN, 16CH and so on
StarTrekker 8-channel module (FLT8) – 8 channels, each pattern stored as two 4-channel patterns
Soundtracker module (15 samples) – the first modules, 1987 to 1989: 15 samples and no signature
ProTracker 3.6 module (IFF) – an IFF wrapper around a module, with version, song information and a comment

.MOD File Format

Introduction

Structure

VERS: the version

INFO: the song

CMNT: author and comment

PTDT: the module

Also used for

Variants

Links

Software

Developers

Reference