Techy stuff from Wikipedia: https://en.wikipedia.org/wiki/Technical_features_new_to_Windows_Vista#Audio_stack_architecture
and from Microsoft: https://msdn.microsoft.com/en-us/library/windows/desktop/dd371455(v=vs.85).aspx
and some more: http://www.thewelltemperedcomputer.com/KB/WASAPI.htm
And from the Audacity Manual: https://manual.audacityteam.org/man/device_toolbar.html#host
WC