Tempo Marks

[Adrian Oehm]

I'm sure I've read this in the manual somewhere, but cannot re-find it...

I have a piece of music set for SATB with Organ accompaniment.  What I would 
like is to have the tempo (metronome) marks printed above both the SATB line 
(currently set using ChoirStaff) and above the Organ line (set with PianoStaff, 
with an extra line for pedals).

If I set \tempo 4 = 100 in the organ part, it appears above the SATB part.

How do I get a tempo mark above both the SATB line (ChoirStaff) and the Organ 
line (PianoStaff)?

Thanks in advance

Adrian