Pass MainSoundConfiguration object rather than a string.

Pass MainSoundConfiguration object rather than a string.

I guess originally it was a string mostly because it's not very well defined,
and Interop seemingly does whatever it wants.  This basic change also means
that things are checked more carefully, and so we must be more relaxed with
some things seen in the wild that I can't find contradictions for in the
standard (and also with the case of channel IDs, which does seem to be
mentioned in the standard).