alternate time sigs

[David Bobroff]

I'd like to do this:

http://notendur.centrum.is/~bobroff/lily/vartime.png

Now, I figure I can handle the "invisible" changes between 9/8 and 3/4
by using \compressMusic or \times as necessary.  I'm guessing that the
compound time signature hack could serve as a model for the displaying
the time signature as it is in the above example, but I only about half
understand how that all works.

Insights/comments/suggestions are welcome.

-David