The tutorial for this project (to re-create it yourself) can be found here.
But! If you're just wanting to see how a replacement to HTML5 Audio and other third-party embeds (like SoundCloud) are built, clone away and mess around with this project here.
Plyr.io Audio Integration (Default Controls)
This is the simplest method of just using plyr.io as a custom audio player to replace HTML5 Audio or a third-party embed, such as SoundCloud.