If the browser can play MP3's then I'll use the audio tag to play a file. If not, I'll have to load in a flash player.
var audio = document.createElement("audio"),
canPlayMP3 = (typeof audio.canPlayType === "function" &&
audio.canPlayType("audio/mpeg;codecs=mp3") !== "");
Edit:
If you don't want to use JavaScript (yes, this will work in browsers that support <audio>
but not MP3), try this:
<audio controls="controls">
<source src="some-audio-file.mp3" type="audio/mpeg;codecs=mp3" />
<!-- if you have an Opus version, also include this:
<source src="some-audio-file.opus" type="audio/ogg;codecs=opus" />
-->
<!-- flash object goes here -->
</audio>
If you want auto-play, include an autoplay
attribute on the audio element.