Technical Notes: As of this writing, Apple’s iPads and iPhones do not seem to support playing midi files. However, after some research, I find that there is an app for that; Sweet Midi, from Roni Music, the same folks who brought you Amazing Slow Downer. It will actually do much more than play midi files on your Apple tablet or phone, but that alone is worth the modest price of the app.
Also, unlike Firefox and Internet Explorer, in Chrome, links to .midi (or .mid) files don’t open a player but offer only to let you download the file. which you can then open in QuickTime, Windows Media Player and most other desktop players.
OR, if you’re on an Apple computer with macOS Catalina 19.15 or later, it won’t play midi files. BUT, VLC is free and plays MIDI files on Mac (and most other platforms). (Thanks for this information, summitted on the Suggestion Form.) Or download and install MIDIPlayer X, an inexpensive player. Either will fix this failure of macOS.