https://timbrechbill.com/saxguru/Timidity.php Looks like the default soundfont is TimGM6mb.sf2 . But maybe it does not come with a default, and the default is only used with the official installer. I installed Timidity++ on my Archlinux based system and I do not get an audio from it too. Archlinux recommends to configure the setting to point it to the soundfont: https://wiki.archlinux.org/title/Timidity%2B%2B

ffplay maybe uses its own configuration to load a specific soundfont. That's why you get it there. Maybe. I don't know how ffplay functions.

No, Timidity++ is not a soundfont, it's a synthesizer: https://en.wikipedia.org/wiki/TiMidity++

So, your installation found that Timidity++ was available and used it to synthesize the required sounds, no sound font needed (TiMidity itself can make use of available sound fonts though).

Note: I can't share the specific MIDI file I was using as it's private, but in case it helps find the soundfont, here's a sample of ffplay playing onestop.mid from Windows ME. It sounds like chiptune at first, but after using the private MIDI file I can confirm that it isn't chiptune. The piano patch sounds kinda like an organ?

Here's a link to the onestop sample (Warning: it becomes ear grating after about 20 seconds due to ffplay misinterpreting percussion as notes; this is why I chose this specific song): https://files.catbox.moe/2ecdhq.mp3

This is what ffplay says when it plays onestop.mid: https://pastebin.com/SVuJai0H

FluidGM is a popular soundfont to bundle with distros, but in the case of Arch I'm not sure. I'll try out the package later, i might be able to tell.