ZynAddSubFX is a free polyphonic and multi-timbral software synthesizer for GNU / Linux, Mac OS X and Microsoft Windows. It is controlled via MIDI. For the generation of the sound software additive, subtractive, and Fourier - sound synthesis used. In addition, various classical effects are applicable. ZynAddSubFX allows micro-intervals up to 128 notes per octave and the simulation of alternative tunings. Under Linux ZynAddSubFX is compatible with the JACK sound server.

Since its first publication in 2002 ZynAddSubFX is developed by Paul Nasca.