Playing a Sound Loop... How?

I am trying to get a feel for SVG. Can you please help me (or point
me to useful documentation or tutorial) for playing a loop with an
on/off button.

I have this code already:

__________
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
    "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">

<svg xmlns:a="http://www.adobe.com/svg10-extensions" a:timeline="independent">
  <a:audio xlink:href="hploop.mp3" begin="0s" />
  <circle id="play" cx="25" cy="25" r="10" fill="red"/>
</svg>
__________

My question is: What attributes must I include to make the sound
loop? I have tried loop="infinite" but it doesn't work. I couldn't find
any documentation from Adobe.Com.

Furthermore, how can I "pause" the loop so to give the impression
it has been muted when you click on the circle?

Thanks for any help or links that anybody provides. A link to a
complete tutorial would be great! Hope I am not posting in the
wrong place.