Thanks for finding this! It's been accepted for a while. At the moment, there are two ways around not currently having this feature. The first is to - through HTML in page scripts - have the music auto-play when you open a page. The only problem with this method is that the music will reset each time you click a link. The alternative is to have a HTML link within your storygame to a separate page (out of the storygame) containing the music file, so that it will continue playing while the reader plays through the storygame.
