Module files (MOD music, tracker music) are a family of music file formats originating from the MOD file format on Amiga systems used in the late 1980s. Those who produce these files (using the software called music trackers) and listen to them, form the worldwide MOD scene, a part of the demoscene subculture.
The mass interchange of "MOD music" or "tracker music" (music stored in module files created with trackers) evolved from early FIDO networks. Many websites host large numbers of these files, the most comprehensive of them being the Mod Archive.
Nowadays most module files, including ones in zipped form, are supported by most popular media players such as Winamp, VLC, Foobar2000, Amarok, Exaile and many others (mainly due to inclusion of common playback libraries such as libmodplug for gstreamer).
Module files store digitally recorded samples and several "patterns" or "pages" of music data in a form similar to that of a spreadsheet. These patterns contain note numbers, instrument numbers, and controller messages. The number of notes that can be played simultaneously depends on how many "tracks" there are per pattern.
A disadvantage of module files is that there is no real standard specification in how the modules should be played back properly, which may result in modules sounding slightly different in different players. This is mostly due to effects that can be applied to the samples in the module file and how the authors of different players choose to implement them. However, tracker music has the advantage of requiring very little CPU overhead for playback, and is distributed as open-source and executed in real-time, allowing composers to control and manipulate sound samples in almost limitless ways to produce music.
Each module file format builds on concepts introduced in its predecessors.
The process of composing module files, known as tracking, is a skillful activity that involves a much closer contact with musical sound than conventional composition, as every aspect of each sonic event is coded, from pitch and duration to exact volume, panning, and laying in numerous effects such as echo, tremolo and fades. Once the module file is finished, it is released to the tracker community. The composer uploads the new composition to one or more of several sites where module files are archived, making it available to his or her audience, who will download the file on their own computers. By encoding textual information within each module file, composers maintain contact with their audiences and with one another by including their email addresses, greetings to fans and other composers, and virtual signatures.