My mistake. I keep forgetting what "quaver" means! Assuming the interpretation in my first example was correct, my second example should have looked like this in measure 2:...

Here you go: http://forum.makemusic.com/attach.aspx/18582/TimeChange.jpg This approach is slightly different from Gareth's. Instead of his "fake measure", I use a "fake time signature".

Ah yes, of course.

Here you go: http://forum.makemusic.com/attach.aspx/18450/GbMajor.jpg

It is as if the keyboard is somehow doubled with the expression controller.