In the 1990s, MIDI's of every variety played in the background. Now in Neocities, a hosting-site that aims to replicate the feel of the times of yor, the only 2 ways that i'm aware of is Midi.js and this way. Midi.js is the more pure kind of way to put music into your site but I myself could'nt get it to work. I'm only putting this here becuase it was harder than I thought to put these background songs into only 1 page. If anyone else stumbles into here - here's the code. Works on Chrome.
Hopefully this helps.