Read original post at John's Blog
I’m still working away on my latest Windows App Store app, and one of the features I wanted to make sure to support was background audio: that is, I wanted the app to still play music when it was snapped to the side of the screen, or even pushed to the back when another app was launched. I found there was plenty of information about on the web, but because things changed a little from the progression from Windows 8 Preview to Windows 8 to Windows 8.1, they documentation I found was of varying degrees of usefulness.