Put an <audio> element on your page.
Get your audio element and call the play() method:
document.getElementById('yourAudioTag').play();
Check out this example: http://www.storiesinflight.com/html5/audio.html
This site uncovers some of the other cool things you can do such as load(), pause(), and a few other properties of the audio element.
When exactly you want to play this audio element is up to you. Read the text of the button and compare it to "no" if you like.
http://www.schillmania.com/projects/soundmanager2/
SoundManager 2 provides a easy to use API that allows sound to be played in any modern browser, including IE 6+. If the browser doesn't support HTML5, then it gets help from flash. If you want stricly HTML5 and no flash, there's a setting for that, preferFlash=false
It supports 100% Flash-free audio on iPad, iPhone (iOS4) and other HTML5-enabled devices + browsers
Use is as simple as:
<script src="soundmanager2.js"></script>
<script>
// where to find flash SWFs, if needed...
soundManager.url = '/path/to/swf-files/';
soundManager.onready(function() {
soundManager.createSound({
id: 'mySound',
url: '/path/to/an.mp3'
});
// ...and play it
soundManager.play('mySound');
});
Here's a demo of it in action: http://www.schillmania.com/projects/soundmanager2/demo/christmas-lights/