MOD music file
Module file (MOD music, tracker music) Amiga MOD music files - music stored in module files created with trackers.
MOD files originated on the Amiga, but because of their flexibility and the extremely large number of MOD files available, MOD players are now available for a variety of machines (IBM PC, Mac, Sparc Station, etc.)
The samples in a MOD file are raw, 8 bit, signed, headerless, linear digital data. There may be up to 31 distinct samples in a MOD file, each with a length of up to 128K (though most are much smaller; say, 10K - 60K). An older MOD format only allowed for up to 15 samples in a MOD file; you don't see many of these anymore. There is no standard sampling rate for these samples.
The sequencing information in a MOD file contains 4 tracks of information describing which, when, for how long, and at what frequency samples should be played. This means that a MOD file can have up to 31 distinct (digitized) instrument sounds, with up to 4 playing simultaneously at any given point. This allows a wide variety of orchestrational possibilities, including use of voice samples or creation of one's own instruments (with appropriate sampling hardware/software). The ability to use one's own samples as instruments is a flexibility that other music files/formats do not share, and is one of the reasons MOD files are so popular, numerous, and diverse.
15 instrument MODs, as noted above, are somewhat older than 31 instrument MODs and are not (at least not by me) seen very often anymore. Their format is identical to that of 31 instrument MODs except:
- Since there are only 15 samples, the information for the last (15th) sample starts at byte 440 and goes through byte 469.
- The songlength is at byte 470 (contrast with byte 950 in 31 instrument MOD)
- Byte 471 appears to be ignored, but has been observed to be 127. (Sorry, this is from observation only)
- Byte 472 begins the pattern sequence table (contrast with byte 952 in a 31 instrument MOD)
- Patterns start at byte 600 (contrast with byte 1084 in 31 instrument MOD)
