The page in question: http://ift.tt/1HmbYXr (it's tiny, might be worth looking at the source directly)

For the sake of future visitors, here's a permalink to the version under discussion on GitHub: http://ift.tt/1HmbYXt

Here's the important bit:

<audio autoplay loop>
<source type=audio/mpeg src=plump.mp3>
<source type=audio/ogg src=plump.ogg>
</audio>

I'm using this specific configuration of <audio> and <source> because I'd previously been informed it was the optimal one for compatibility. The mp3 and ogg files are both valid, and both are served with the correct Content-Type headers (audio/mpeg and audio/ogg).

It works fine in Firefox and Chrome, but not in Safari (OS X Yosemite), nor Mobile Safari (iOS 8.1). If I go into the Safari developer tools, select the audio element and do $0.play(), it doesn't work either.

Any idea what's up?

Thanks in advance!