Qsynth - Qsynth is a simple Qt4 application wrapper for the ...
Cantabile - Plugin host for live performance.
VirtualMIDISynth - VirtualMIDISynth is a software MIDI synthesizer implemented as a Windows multimedia user driver...
Gig Performer - Gig Performer is a cross-platform audio plugin host for live music performances
ZynAddSubFX - ZynAddSubFX is an open source software synthesizer for Linux, Mac OS X and Microsoft Windows.
Blue Cat's PatchWork - Blue Cat's PatchWork is a universal plug-ins patchbay and multi FX that can host up to 64 VST, VST3, Audio Unit or built-in plug-ins into any Digital Audio Workstation (DAW) in a single instance, with both serial and parallel routing options.