WaveShop - Open source audio editor

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.

TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.

SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).

SoundEngine - Freeware audio editor/recorder

Cubasis - Cubasis is Steinberg’s streamlined, multitouch sequencer for the iPad.