FluidSynth

 is a software MIDI synthesizer which uses collections of samples in the format to render MIDI music.

FluidSynth is available as an option for MIDI playback in the following source ports:
 * GLBoom+ and PrBoom+
 * GZDoom and ZDoom

In addition, Doom64 EX uses FluidSynth exclusively for audio playback. Its WadGen utility creates a custom sound font, which is used for both sound effects and Doom 64's ambient music. (Using this soundfont with MIDI tracks created for instruments will sound odd.)

SLADE 3's MIDI playback is also dependent on FluidSynth.