MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .
Schism Tracker - Schism Tracker is a free reimplementation of Impulse Tracker, a program used to create high quality...
GoatTracker - This is a crossplatform C64 music editor.
OpenMPT - OpenMPT is a popular tracker software for Windows.
PxTone Collage - A music editing software, capable of using common sounds, custom sounds, and everything in between to make surprisingly good music. Originally in Japanese, but easily fixed.
DefleMask - An old-school game music tracker for an ample variety of systems.