Surge XT - Open-source subtractive-hybrid synthesizer formerly sold commercially as Vember Audio Surge.
MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .
ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
OpenMPT - OpenMPT is a popular tracker software for Windows.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
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.