SoundTracker is a music tracking tool
It is a very cool program for creating digital music.
Samples can be lined up on tracks and patterns which are then arranged to a song. Supported module formats are XM and MOD; the player code is the one from OpenCP. A basic sample recorder and editor is also included. SoundTracker is free ("open source") software, licensed under the GNU GPL.
The name of the program is a tribute to Karsten Obarski, who released his SoundTracker program for the Amiga in 1987 and thus unknowingly founded the basis of a huge free music movement which developed in the following years and which is still going strong.
The basic concept is very simple: you have a number of sound samples, and you can arrange them on so-called tracks. A track (also called "channel") can not play more than one sample at the same time. Whereas the original Amiga trackers only provided four tracks (this was the hardware limit), modern trackers can mix a virtually unlimited number of channels into one sound stream, applying various effects to the samples used.