Dexed - Dexed is a multi-platform, multi-format plugin synth that is closely modeled on the Yamaha DX7.
Surge XT - Open-source subtractive-hybrid synthesizer formerly sold commercially as Vember Audio Surge.
ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
Synth1 - Synth1 is a software synthesizer. Functionally it is modeled on the Clavia Nord Lead 2 Red Synth.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
ZynAddSubFX - ZynAddSubFX is an open source software synthesizer for Linux, Mac OS X and Microsoft Windows.