I created a test page using the most basic implementation of the HTML5 audio tag so I could see how modern browsers render the default controls. (You can view my test page here.) As is the case with almost everything browser-related, there is quite a bit of discrepancy in how each browser renders the controls. What’s surprising is how mobile versions of browsers render controls differently from their desktop counterparts.
You’ll also notice that the Native Browser on Android 2.2 (Froyo) doesn’t render the HTML5 audio controls at all. This is a known issue with Froyo and should be fixed in Android 3. Update: Read more about this here.
Take a look at how each browser renders HTML5 audio controls below: