SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
KORG Gadget - KORG Gadget - From iOS to Mac. Music production software to help your musical imagination become reality.
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.
Poison-202 - Vintage MIDI synthesizer for Mac and iOS
MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.
KORG iMS-20 - KORG iMS-20: Transform your iPad into a complete analog synth studio!