top-line tempo text markings

[D Josiah Boothby]

I recall a thread on this subject a few months ago, but I have not been
able to find it in the archives. 

I'm trying to create a tempo marking -- something like "Andante" -- that
only shows in the top line of a score, but when parts are extracted,
shows on all of the parts. Similar to a rehearsal mark, but
left-justified at the beginning of the bar where it begins. I'd do a
simple text markup but can't figure out how to make it behave like a
rehearsal mark. 

I've tried doing a \mark \markup, but trying to make it justify left
didn't work. 

Josiah