SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
keezy - A colorful soundboard. Play with music.
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.
Splice - Music creation, collaboration, and sharing made simple.
MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.