>>
> I believe the issue here is that the barline is considered to _begin_ the
> new measure rather than end the old one. I can't think of a way around
> this except what James suggests. (Then there's the issue of the staff
> lines underneath the bar line, to which I don't have a ready answer.)
>
>
I don't think it's an issue.
it's a question of timing - both voices define a bar at the same time (part
3 the initial bar which usually is not displayed at the beginning of a
system) and its properties and - as usual - the latest wins.
Yes, good point. I didn't realize that \startStaff is actually creating a new staff, in this case joined to the one before on the same line.
-David