This is an example of Storyline 2 audio controls (Flash and HTML5). The controls contain Mute, Volume change (via slider), rewind audio to the beginning, Play/Pause toggle, audio progress indicator and Closed Captions for good measure. Its an old post, but maybe some might still find this useful.
I built on an existing Steve Flowers flash file, but changed the direction of the communication with the Flash file (Javascript calls the flash function).
It is tested in IE Edge (Flash and HTML5) , Win Chrome (HTML5) , iOS and Mac Safari (HTML5), Pixel Chrome (HTML5) so far.
Live example: https://dl.dropboxusercontent.com/u/7158763/HTML%20and%20SWF%20Volume%20Controls%20-%20Storyline%20output/story.html
*.STORY and *.FLA attached to this post.