If MIDI is a problem (and it has been so here for a long time), then the ONLY other choice is ABC. Until solfa or jianpu has reliable webpages or applications to play it, they are just "not ready for prime time". (I dearly hope that jianpu never does: it's AWFUL!!!)

I would like to see something like the pages at The Session. Here is . The Longest Name isn't on the site.

The real question is why MIDI doesn't work. MIDI players are built-in to Windows, Mac, and Android (yes, Android!). I don't know about iPhone and I would assume they are NOT built-in to Unix/Linux, but there are certain to be dozens of players available for download. Most web browsers know how to deal with MIDI natively.

'For the fun of it', try going to BitMIDI. Select a song and click its link or click the Random MIDI button at upper right. Try ...
1) Click the link to download the song (below the button at the right). Once it completes the download, simply double-click the file. Does it play?
2) Click the link (below the button at the left) to play the song online. Does it play?

For me, BOTH methods worked in Windows, using Firefox (version 125.0.1) and using Google Chrome (version 124.0.63761.61), and on my Android, using the built-in "Samsung Internet" (version 242.0.7.1). And no, I've never explicitly installed any kind of MIDI player; it is built-in to Windows and the browsers can normally play them without any problem.

BB,
NightWing