The code uses two different methods for Internet Explorer (IE) and Firefox (FF).
For IE, it uses an object tag and the object model to initiate playback with player.controls.play and stop. Note the assignment of the source URL and data, this allows you to change which audio (or video) is being played.
The FF approach uses a pop up, opened with window.open. This loads a very small page which includes the player tag. The pop up is named, so later requests will reload the same window.
The template uses $bFF as a flag to indicate whether to deliver the page content for IE or FF. $bFF is true if the user agent is Firefox, false otherwise. The template logic can be replaced with PHP.
Difficulties were encountered playing HTTPS audio with a self-signed certificate under FF. After research, the simplest resolution was to route audio requests through HTTP.
For MP3s, you can use: http://docs.dojocampus.org/dojox/av/FLAudio