two dynamics contexts and moving my headers

[James E. Bailey]

Hello,

I was having some difficulty yesterday, and I'm sure that it's only  
because I'm in a rush and can't think well, but this just isn't  
working for me.
1) I have a ChoirStaff and PianoStaff. I want dynamics above the  
ChoirStaff and centered between the PianoStaff. No matter how hard I  
try, it just doesn't work for me. I get errors of really strange  
natures and the end effect is that I don't get what I was looking for.  
I'm sure exactly what I need is somewhere on the LSR, but the LSR only  
likes me if I know exactly what's there, otherwise, I don't really  
find what I'm looking for. Help?

2) my composer and poet tags are in the wrong place! I should say,  
when I add \center-align, it moves them to the right, even if the  
markups are only one line? I'm guessing that it's centering the  
markups to the page and not to itself. Can I get the markups to be  
where they are normally, but to have two lines that are centered to  
each other. I'm trying \markup {\center-align {"James E. Bailey"  
\smaller "2008"}}. Nothing fancy.