.MOD File Format

Introduction

StarTrekker was an Amiga tracker by Bjørn Wesen (Exolon of Fairlight). Its version 1.0, of 14 July 1990, brought 8 channels to the Amiga module, and with them the FLT signatures: FLT4 for ordinary 4-channel modules, and FLT8 for 8-channel ones. Later versions, 1.2 and 1.3, added synthesised AM and FM sounds. EXO8 is read the same way as FLT8.

The header is the same as a ProTracker module’s, but the 8-channel patterns are not stored as 8-channel rows. Each one is kept as two ordinary 4-channel patterns, one after the other: the even-numbered one holds channels 1 to 4, and the next one channels 5 to 8. The order table names the even pattern of each pair. A reader that takes FLT8 as 8 channels per row, as for 8CHN, plays nonsense, and one that takes it as 4 channels plays each pair as two halves one after the other: this is a separate format. (FLT4 files are laid out like M.K. ones and are read as ProTracker modules.)

No file of this format was among the files examined for this site; the explorer’s parser was tested with files built for the test, from OpenMPT’s description of the layout.

A .mod file dropped on any page of this site opens in the explorer, which shows the header field by field, the samples, the order list and every pattern pair note by note, as 8 channels, and plays the song.

Structure

A 1,084-byte header, then the stored 4-channel patterns, then the sample data, with nothing between them. All numbers are big-endian.

Telling it apart

The explorer’s parser for this format checks two things: the file is at least 1,084 bytes long, and the four bytes at offset 1080 are FLT8 (46 4C 54 38) or EXO8 (45 58 4F 38). A file with any other bytes there is turned down, and the explorer tries the parsers for the other module formats.

Everything after the signature is read as it comes. An odd number among the played positions of the order table is reported as a problem, since every entry should name the first pattern of a pair; so are the faults any module can have, such as a volume above 64 or a file cut short.

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 1 to 32 channels, 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

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