James Clarke turned me on to the fact that modifying the Expression Encoder templates is trivial.  I tweaked the AudioGrey template to turn off autoplay and changed the default volume.  Of course, one could even take this further and really modify the templates, which Tim Heuer has a great post on.  So, this makes for a streamlined workflow for getting audio (or video) onto your blog.  The pieces of the puzzle:

Expression Encoder

Silverlight Streaming Publishing Plug-in

Silverlight Streaming Account

Windows Live Writer

Silverlight Streaming Live Writer Plug-in

The net result: here's the audio player playing my composition hill.climb embedded in this blog post: