Sonic Pi - Sonic Pi is a new kind of instrument for a new generation of musicians. It is simple to learn, powerful enough for live performances and free to download.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
SuperCollider - A real time audio synthesis engine, and an object-oriented programming language specialised for...
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.
ChucK - A strongly-timed music programming language
MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.