Play mp3 files via HTML5 on Firefox Mac, alternatives

Play mp3 files via HTML5 on Firefox Mac, alternatives

I need to play an mp3 file; something like
var sound = new Audio('http://.......'); snd.play();
does work in Chrome and Firefox on Windows but not in Firefox on Mac, can
you confirm it is the normal behaviour?
From here: https://bugzilla.mozilla.org/show_bug.cgi?id=799318 it seems
that on Mac the feature has been just added (so probably the current
release of Firefox doesn't provide it) but there are a lot of messages
about and I'm a bit confused...
Is it normal that if I just put the mp3 URL in the URL bar it works?
So if you confirm that it is the normal behaviour can you tell me which
are the alternatives? 1) flash fallback ? 2) convert mp3 to oog (supported
by firefox) on the fly?
Can you explain how to implement both?
Thanks.