Ocean beta - Make music with friends in your browser
Cubasis - Cubasis is Steinberg’s streamlined, multitouch sequencer for the iPad.
iO-808 - Rhythm composer modeled after Roland's TR-808 drum machine.
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.
Music Box Fun - Make and share music box songs online
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).