ZDoom offers a variety of software synthesizers for MIDI playback, which make using custom MIDI instruments possible. They can be selected through the MIDI device entry of the sound options menu. In addition to whatever MIDI devices are offered by the operating system used, these five choices are available:
MIDI music does not contain raw sound data, instead it only contains instructions for instruments. The synthesizer creates sound from these instructions; and different synths will produce very different sounds from the same MIDI input. Most synths operate either by using a collection of samples or through frequency modulation; in ZDoom's case, the OPL emulator uses FM synthesis while the others use collections of samples referred to as sound fonts.
On Windows systems, three synthesizers should work right out of the box: the FMOD synth, the OPL emulator, and the Windows-provided wavetable synth. Other synths will require to be set up and configured: ZDoom itself is not provided with any sound font, and furthermore two of the synthesizers are not provided directly with ZDoom and need to be downloaded separately. Please refer to each synth's article for specific instructions on how to install and configure them.
- Note: information about the Linux or MacOS equivalents would be welcome.
ZDoom can use any synthesizer set up as a MIDI driver. Typically, there will be only one (e.g. "Microsoft GS Wavetable SW Synth" on all Windows systems since DirectMusic was developed), but additional ones can be present. Some global synthesizers that you may try to add to your system as alternatives to the ZDoom synths include:
- BASS MIDI driver, for Windows systems ( )
- TiMidity++ Windows Synth, for Windows systems (more information)
- Virtual MIDI Synth, for Windows systems
- Yamaha S-YXG50 SoftSynthesizer, for Windows XP systems (not compatible with Vista/7/8/etc.) (more information)
- MIDI Yoke and LoopBe1, for Windows systems, both allow to redirect MIDI output to any MIDI application rather than to a normal driver.