ZynAddSubFX (also now called Zyn-Fusion) is a free and open-source software synthesizer for Linux, Mac OS X and Microsoft Windows.

[2] For sound generation it has three hybrid synth engines that combine additive, subtractive, Fourier and other synthesis methods.

The synthesizer has effects like reverberation, echo, chorus, distortion, equalization and others, and supports microtonal tunings.

[3][4] The original author of ZynAddSubFX is Romanian programmer Nasca Octavian Paul.

Slavonic pagan ambient project Svitlo albums were created using ZynAddSubFX as synthesizer.