Configuring Soundfonts / Playing MIDI files

My music player (Quod Libet, flatpak) shows this error any time it tries to play a MIDI file, and I'm at my wit's end figuring out how to solve it. I might in theory be able to configure its GStreamer pipeline manually, as it has a field for that in the preferences, but I wouldn't even know where to start with that, as the only way to get the default pipeline is by launching it in debug mode, which I don't know if I can do with the flatpak. Web search tells me audio/x-midi-event decoder is related to soundfonts, but searching for info on how to configure soundfonts in Linux generally, let alone in Fedora Atomic, has so far turned up little more than technical documentation that makes no sense due to lacking context that I, a non-expert, do not have. I have a folder of soundfonts I used in Windows, but not the knowledge of how to point fluidsynth or GStreamer or whatever it is at one of them. I'm not sure any of the music players I've tried so far have actually played MIDI files out of the box. Some of them have config options to manually specify a soundfont to use, and MIDIs worked there when I set that, but Quod Libet doesn't have such a setting, so I have to figure out another way. I'd really appreciate some help figuring this out.

Managing soundfonts — soundfonts

FluidSynth requires a soundfont to synthesize a midi. On Linux distributions some soundfonts are often preinstalled, though their quality varies. If your midi sounds very poor, try using another soundfont.