That github midi player is a pain in the ass and I AM DONE trying to get it to work on my website. Between trying to implement this spaghetti-@$$ code and just having people download my MIDIs and play them in VLC, I'll take VLC.
Ack! >_< I just now discovered I forgot to set the Pizzicato preset of my new soundfont to C0! You can easily fix this in Polyphone, which I'll do when I come back from errands today.
It wouldn't be so bad if the default soundfont were configured properly. But it was plainly made by programmers, not musicians.