DefleMask - An old-school game music tracker for an ample variety of systems.

OpenMPT - OpenMPT is a popular tracker software for Windows.

FamiStudio - FamiStudio is very simple music editor for the Nintendo Entertainment System or Famicom. It is designed to be easier to use than FamiTracker, but its feature set is also much more limited.

SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).

MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .

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.