Perhaps even better: don't use the \\ but explicitly
instantiate one of the voices
(related to a recent email discussion).
When I removed the \\, I got errors about clashing columns. I'll
check into the explicit voice instantiation thing. For now I like
the \oneVoice solution for this example.
The \oneVoice solution did not work for the example from GDP I'm
working on, though. The autobeaming still doesn't appear. Here's
the original code and then the fix I made for it. In James'
example, the \oneVoice fixed stem direction and autobeaming. In
this example, there was no problem with stem direction to begin
with, just with autobeaming. If you see a more elegant way please
share :)