Here is an article that describes how audio works in WinRT. I thought I post it here in case Jules wants to examine what's needed for WinRT support:
Real-time Audio in Windows Store and Windows Phone Apps - http://blogs.windows.com/windows/b/buildingapps/archive/2014/05/15/real-time-audio-in-windows-store-and-windows-phone-apps.aspx
WASAPI is supported so there may be not that much to do on the audio side :-)