Also as an actual answer I couldn't peg a decade or year because it sounds like every MIDI file ever played on a Pirated video game installation.
To embed a webm or mp4 file you do it the same way you would embed an image. 
is the code for this embedded video, for example. So, 
or something like that. It does not work on all mobile apps for Lemmy, most notably Jerboa breaks the embed.