I’m unable to access your site as it shows the site can’t be reached check the screenshot: http://prntscr.com/onr0ts
And about the mp3 both doesn’t seem to be like ended with proper file extension. Please upload the mp3 in your media of site & then try to paste the link in theme option so that it works properly. Checkout the screenshot: http://prntscr.com/onr1xy how we actually uploaded our mp3 file. Let me know if this solves your issue or not.