FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.
FluidSynth - FluidSynth is a real-time software synthesizer based on the SoundFont 2 specifications and has...
AudioTool - Whether you want to make music for the club, or you're aiming to put a few tracks to a film, Audiotool is a website geared towards putting the mixes at your fingertips. Read more about AudioTool.
VirtualMIDISynth - VirtualMIDISynth is a software MIDI synthesizer implemented as a Windows multimedia user driver...
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Zebralette - u-he makes creative software synthesizers and effects.