Vital is a spectral warping wavetable synthesizer with drag'n'drop modulation workflow and animated preview of the synth's inner workings where needed. Comes with many modulation sources (including audio-rate), MPE support and FX chain.
Surge is an open source digital synthesizer originally written and sold as a commercial product by @kurasu (Claes Johanson) at Vember Audio. The synth uses subtractive hybrid synthesis and each patch contains two 'scenes' which are separate instances of the entire...
Dexed is an FM-type softsynth developed by Pascal Gauthier of Digital Suburban. It is an ideal application for importing, playing and editing/managing sysex patches from both the classic Yamaha DX7 synthesizer and the TX7.
Helm is a free, cross-platform, polyphonic synthesizer with a powerful modulation system. Helm runs on GNU/Linux, Mac, and Windows as a standalone program or LV2/VST/VST3/AU plugin.
Skale Tracker is a music tracker (a special kind of music sequencer) available for Windows and Linux on the desktop as well as in a Flash-based browser verison.Discontinued
Online version is no longer available. Last desktop version, v0.81, released on December 2005, it's still downloadable and usable.
FluidSynth is a real-time software synthesizer based on the SoundFont 2 specifications and has reached widespread distribution. FluidSynth itself does not have a graphical user interface, but due to its powerful API several applications utilize it and it has even found its way...