Help with understanding HTML5/JavaScript mp3 jukebox

I’m working on a personal project for my portfolio, and I’m trying to emulate the functionality of this site: http://thisweeksplaylist.co[1] . I couldn’t understand their minified footer.js file, which seems to be the music player (they also have a header.js, not sure if it’s part of what I’m missing). I’m having a hard time finding a tutorial anywhere that covers all the functionality their music player has.

I’m also confused by their HTML markup. I don’t understand how the JavaScript is interpreting the <li audio=""> elements.

Particular functionality I want to include but am unsure about is making each <li>'s background a song progress trackbar. It was easy enough to make an array in JS that handles normal <audio src=""> elements, but the particular combination of functionality and markup that is used here has me baffled.