TiMidity

Tuukka Toivonen wrote TiMidity in 1995. The idea was simple: rather than sending MIDI to a sound card with an onboard synth, compute the waveform on the CPU and play it back as ordinary digital audio — or write it out as a WAV file. Instruments came from patch files in the same format the Gravis UltraSound used, so ready-made sound banks existed from day one.

When Toivonen stopped maintaining it, Masanao Izumo and others picked it up as TiMidity++, adding SoundFont support among much else. Through the 2000s it was the standard answer to "why are my MIDI files silent on Linux?". FluidSynth has since taken over much of that role, but TiMidity++ is still sitting in the package repositories.