MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.
OnlineSequencer.net - OnlineSequencer.net is an online music sequencer that allows users to create beats and music tracks.
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.
GoatTracker - This is a crossplatform C64 music editor.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
Jummbox - A modified Beepbox that have more stuff then Beepbox. It can be used just like Beepbox. The features of Jummbox is the same of Beepbox's features, but Jummbox have more stuff to offer.